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[PATCH v2 0/3] selftests/mm: hugetlb cgroup charging: robustness fixes

by Li Wang

Changes in v2: - 1/3: Parse -s using sscanf("%zu", ...) instead of strtoull(). - 2/3: Fix typo in charge_reserved_hugetlb.sh ("reseravation" -> "reservation"). - 3/3: No changes. This series fixes a few issues in the hugetlb cgroup charging selftests (write_to_hugetlbfs.c + charge_reserved_hugetlb.sh) that show up on systems with large hugepages (e.g. 512MB) and when failures cause the test to wait indefinitely. On an aarch64 64k page kernel with 512MB hugepages, the test consistently fails in write_to_hugetlbfs with ENOMEM and then hangs waiting for the expected usage values. The root cause is that charge_reserved_hugetlb.sh mounts hugetlbfs with a fixed size=256M, which is smaller than a single hugepage, resulting in a mount with size=0 capacity. In addition, write_to_hugetlbfs previously parsed -s via atoi() into an int, which can overflow and print negative sizes. Reproducer / environment: - Kernel: 6.12.0-xxx.el10.aarch64+64k - Hugepagesize: 524288 kB (512MB) - ./charge_reserved_hugetlb.sh -cgroup-v2 - Observed mount: pagesize=512M,size=0 before this series After applying the series, the test completes successfully on the above setup. Li Wang (3): selftests/mm/write_to_hugetlbfs: parse -s as size_t selftests/mm/charge_reserved_hugetlb.sh: add waits with timeout helper selftests/mm/charge_reserved_hugetlb: fix hugetlbfs mount size for large hugepages .../selftests/mm/charge_reserved_hugetlb.sh | 51 ++++++++++--------- .../testing/selftests/mm/write_to_hugetlbfs.c | 9 ++-- 2 files changed, 34 insertions(+), 26 deletions(-) -- 2.49.0

1 week, 3 days

[PATCH v1 1/3] selftests/mm: fix va_high_addr_switch.sh return value

by Chunyu Hu

Patch series "Fix va_high_addr_switch.sh test failure - again", v1. There are two issues exist for the va_high_addr_switch test. One issue is the test return value is ignored in va_high_addr_switch.sh. The second is the va_high_addr_switch requires 6 hugepages but it requires 5. Besides that, the nr_hugepages setup in run_vmtests.sh for arm64 can be done in va_high_addr_switch.sh too. This patch: (of 3) The return value should be return value of va_high_addr_switch, otherwise a test failure would be silently ignored. Fixes: d9d957bd7b61 ("selftests/mm: alloc hugepages in va_high_addr_switch test") CC: Luiz Capitulino <luizcap(a)redhat.com> Signed-off-by: Chunyu Hu <chuhu(a)redhat.com> --- tools/testing/selftests/mm/va_high_addr_switch.sh | 2 ++ 1 file changed, 2 insertions(+) diff --git a/tools/testing/selftests/mm/va_high_addr_switch.sh b/tools/testing/selftests/mm/va_high_addr_switch.sh index a7d4b02b21dd..f89fe078a8e6 100755 --- a/tools/testing/selftests/mm/va_high_addr_switch.sh +++ b/tools/testing/selftests/mm/va_high_addr_switch.sh @@ -114,4 +114,6 @@ save_nr_hugepages # 4 keep_mapped pages, and one for tmp usage setup_nr_hugepages 5 ./va_high_addr_switch --run-hugetlb +retcode=$? restore_nr_hugepages +exit $retcode -- 2.49.0

1 week, 4 days

[PATCH v2 RESEND] selftests: hid: tests: test_wacom_generic: add tests for display devices and opaque devices

by Alex Tran

Verify Wacom devices set INPUT_PROP_DIRECT on display devices and INPUT_PROP_POINTER on opaque devices. Moved test_prop_pointer into TestOpaqueTablet. Created a DirectTabletTest mixin class for test_prop_direct that can be inherited by display tablet test classes. Used DirectTabletTest for TestDTH2452Tablet case. Signed-off-by: Alex Tran <alex.t.tran(a)gmail.com> --- Changes in v2: - Removed the tests from the BaseTest class - Removed disabling tests for certain subclasses - Moved test_prop_pointer under TestOpaqueTablet - Created DirectTabletTest mixin class - Moved test_prop_direct under TestDTH2452Tablet .../selftests/hid/tests/test_wacom_generic.py | 30 +++++++++++-------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/tools/testing/selftests/hid/tests/test_wacom_generic.py b/tools/testing/selftests/hid/tests/test_wacom_generic.py index 2d6d04f0f..9d0b0802d 100644 --- a/tools/testing/selftests/hid/tests/test_wacom_generic.py +++ b/tools/testing/selftests/hid/tests/test_wacom_generic.py @@ -598,18 +598,6 @@ class BaseTest: if unit_set: assert required[usage].contains(field) - def test_prop_direct(self): - """ - Todo: Verify that INPUT_PROP_DIRECT is set on display devices. - """ - pass - - def test_prop_pointer(self): - """ - Todo: Verify that INPUT_PROP_POINTER is set on opaque devices. - """ - pass - class PenTabletTest(BaseTest.TestTablet): def assertName(self, uhdev): @@ -677,6 +665,13 @@ class TestOpaqueTablet(PenTabletTest): uhdev.event(130, 240, pressure=0), [], auto_syn=False, strict=True ) + def test_prop_pointer(self): + """ + Verify that INPUT_PROP_POINTER is set on opaque devices. + """ + evdev = self.uhdev.get_evdev() + assert libevdev.INPUT_PROP_POINTER in evdev.properties + class TestOpaqueCTLTablet(TestOpaqueTablet): def create_device(self): @@ -862,7 +857,16 @@ class TestPTHX60_Pen(TestOpaqueCTLTablet): ) -class TestDTH2452Tablet(test_multitouch.BaseTest.TestMultitouch, TouchTabletTest): +class DirectTabletTest(): + def test_prop_direct(self): + """ + Verify that INPUT_PROP_DIRECT is set on display devices. + """ + evdev = self.uhdev.get_evdev() + assert libevdev.INPUT_PROP_DIRECT in evdev.properties + + +class TestDTH2452Tablet(test_multitouch.BaseTest.TestMultitouch, TouchTabletTest, DirectTabletTest): ContactIds = namedtuple("ContactIds", "contact_id, tracking_id, slot_num") def create_device(self): -- 2.51.0

1 week, 4 days

[GIT PULL] kunit fixes update for Linux 6.19-rc3

by Shuah Khan

Hi Linus, Please pull the following fixes update for Linux 6.19-rc3. Drops unused parameter from kunit_device_register_internal and makes FAULT_TEST default to n when PANIC_ON_OOPS. Note: Sending this early for 6.19-rc3 (way too late for rc2 anyways) diff is attached. thanks, -- Shuah ---------------------------------------------------------------- The following changes since commit 8f0b4cce4481fb22653697cced8d0d04027cb1e8: Linux 6.19-rc1 (2025-12-14 16:05:07 +1200) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest tags/linux_kselftest-kunit-fixes-6.19-rc3 for you to fetch changes up to c33b68801fbe9d5ee8a9178beb5747ec65873530: kunit: make FAULT_TEST default to n when PANIC_ON_OOPS (2025-12-15 09:27:19 -0700) ---------------------------------------------------------------- linux_kselftest-kunit-fixes-6.19-rc3 Drops unused parameter from kunit_device_register_internal and makes FAULT_TEST default to n when PANIC_ON_OOPS. ---------------------------------------------------------------- Brendan Jackman (1): kunit: make FAULT_TEST default to n when PANIC_ON_OOPS Uwe Kleine-König (1): kunit: Drop unused parameter from kunit_device_register_internal lib/kunit/Kconfig | 2 +- lib/kunit/device.c | 7 +++---- 2 files changed, 4 insertions(+), 5 deletions(-) ----------------------------------------------------------------

1 week, 4 days

[PATCH 0/3] selftests/mm: hugetlb cgroup charging: robustness fixes

by Li Wang

This series fixes a few issues in the hugetlb cgroup charging selftests (write_to_hugetlbfs.c + charge_reserved_hugetlb.sh) that show up on systems with large hugepages (e.g. 512MB) and when failures cause the test to wait indefinitely. On an aarch64 64k page kernel with 512MB hugepages, the test consistently fails in write_to_hugetlbfs with ENOMEM and then hangs waiting for the expected usage values. The root cause is that charge_reserved_hugetlb.sh mounts hugetlbfs with a fixed size=256M, which is smaller than a single hugepage, resulting in a mount with size=0 capacity. In addition, write_to_hugetlbfs previously parsed -s via atoi() into an int, which can overflow and print negative sizes. Reproducer / environment: - Kernel: 6.12.0-xxx.el10.aarch64+64k - Hugepagesize: 524288 kB (512MB) - ./charge_reserved_hugetlb.sh -cgroup-v2 - Observed mount: pagesize=512M,size=0 before this series After applying the series, the test completes successfully on the above setup. Li Wang (3): selftests/mm/write_to_hugetlbfs: parse -s with strtoull and use size_t selftests/mm/charge_reserved_hugetlb.sh: add waits with timeout helper selftests/mm/charge_reserved_hugetlb: fix hugetlbfs mount size for large hugepages .../selftests/mm/charge_reserved_hugetlb.sh | 49 ++++++++++--------- .../testing/selftests/mm/write_to_hugetlbfs.c | 19 +++++-- 2 files changed, 43 insertions(+), 25 deletions(-) -- 2.49.0

1 week, 4 days

[PATCH v9 00/16] arm64: entry: Convert to Generic Entry

by Jinjie Ruan

Currently, x86, Riscv, Loongarch use the Generic Entry which makes maintainers' work easier and codes more elegant. arm64 has already successfully switched to the Generic IRQ Entry in commit b3cf07851b6c ("arm64: entry: Switch to generic IRQ entry"), it is time to completely convert arm64 to Generic Entry. The goal is to bring arm64 in line with other architectures that already use the generic entry infrastructure, reducing duplicated code and making it easier to share future changes in entry/exit paths, such as "Syscall User Dispatch". This patch set is rebased on v6.18-rc7. And the performance was measured on Kunpeng 920 using "perf bench basic syscall" with "arm64.nopauth selinux=0 audit=1". After switch to Generic Entry, the performance are below: | Metric | W/O Generic Framework | With Generic Framework | Change | | ---------- | --------------------- | ---------------------- | ------ | | Total time | 2.130 [sec] | 2.235 [sec] | ↑4.90% | | usecs/op | 0.213095 | 0.223512 | ↑4.89% | | ops/sec | 4,692,753 | 4,474,044 | ↓4.89% | Compared to earlier with arch specific handling, the performance decreased by approximately 4.9%. On the basis of optimizing syscall_get_arguments()[1], el0_svc_common() and syscall_exit_work(), the performance are below: | Metric | W/O Generic Entry | With Generic Entry opt| Change | | ---------- | ----------------- | ------------------ | ------ | | Total time | 2.130 [sec] | 2.134 [sec] | ↑0.18% | | usecs/op | 0.213095 | 0.213414 | ↑0.15% | | ops/sec | 4,692,753 | 4,685,737 | ↓0.15% | Therefore, after the optimization, ARM64 System Call performance remains almost unchanged. It was tested ok with following test cases on kunpeng920 and QEMU virt platform: - Perf tests. - Different `dynamic preempt` mode switch. - Pseudo NMI tests. - Stress-ng CPU stress test. - Hackbench stress test. - MTE test case in Documentation/arch/arm64/memory-tagging-extension.rst and all test cases in tools/testing/selftests/arm64/mte/*. - "sud" selftest testcase. - get_set_sud, get_syscall_info, set_syscall_info, peeksiginfo in tools/testing/selftests/ptrace. - breakpoint_test_arm64 in selftests/breakpoints. - syscall-abi and ptrace in tools/testing/selftests/arm64/abi - fp-ptrace, sve-ptrace, za-ptrace in selftests/arm64/fp. - vdso_test_getrandom in tools/testing/selftests/vDSO - Strace tests. The test QEMU configuration is as follows: qemu-system-aarch64 \ -M virt,gic-version=3,virtualization=on,mte=on \ -cpu max,pauth-impdef=on \ -kernel Image \ -smp 8,sockets=1,cores=4,threads=2 \ -m 512m \ -nographic \ -no-reboot \ -device virtio-rng-pci \ -append "root=/dev/vda rw console=ttyAMA0 kgdboc=ttyAMA0,115200 \ earlycon preempt=voluntary irqchip.gicv3_pseudo_nmi=1" \ -drive if=none,file=images/rootfs.ext4,format=raw,id=hd0 \ -device virtio-blk-device,drive=hd0 \ [1]: https://lore.kernel.org/all/20251201120633.1193122-3-ruanjinjie@huawei.com/ Changes in v9: - Move "Return early for ptrace_report_syscall_entry() error" patch ahead to make it not introduce a regression. - Not check _TIF_SECCOMP/SYSCALL_EMU for syscall_exit_work() in a separate patch. - Do not report_syscall_exit() for PTRACE_SYSEMU_SINGLESTEP in a separate patch. - Add two performance patch to improve the arm64 performance. - Add Reviewed-by. - Link to v8: https://lore.kernel.org/all/20251126071446.3234218-1-ruanjinjie@huawei.com/ Changes in v8: - Rename "report_syscall_enter()" to "report_syscall_entry()". - Add ptrace_save_reg() to avoid duplication. - Remove unused _TIF_WORK_MASK in a standalone patch. - Align syscall_trace_enter() return value with the generic version. - Use "scno" instead of regs->syscallno in el0_svc_common(). - Move rseq_syscall() ahead in a standalone patch to clarify it clearly. - Rename "syscall_trace_exit()" to "syscall_exit_work()". - Keep the goto in el0_svc_common(). - No argument was passed to __secure_computing() and check -1 not -1L. - Remove "Add has_syscall_work() helper" patch. - Move "Add syscall_exit_to_user_mode_prepare() helper" patch later. - Add miss header for asm/entry-common.h. - Update the implementation of arch_syscall_is_vdso_sigreturn(). - Add "ARCH_SYSCALL_WORK_EXIT" to be defined as "SECCOMP | SYSCALL_EMU" to keep the behaviour unchanged. - Add more testcases test. - Add Reviewed-by. - Update the commit message. - Link to v7: https://lore.kernel.org/all/20251117133048.53182-1-ruanjinjie@huawei.com/ Chanegs in v7: - Support "Syscall User Dispatch" by implementing arch_syscall_is_vdso_sigreturn() as kemal suggested. - Add aarch64 support for "sud" selftest testcase, which tested ok with the patch series. - Fix the kernel test robot warning for arch_ptrace_report_syscall_entry() and arch_ptrace_report_syscall_exit() in asm/entry-common.h. - Add perf syscall performance test. - Link to v6: https://lore.kernel.org/all/20250916082611.2972008-1-ruanjinjie@huawei.com/ Changes in v6: - Rebased on v6.17-rc5-next as arm64 generic irq entry has merged. - Update the commit message. - Link to v5: https://lore.kernel.org/all/20241206101744.4161990-1-ruanjinjie@huawei.com/ Changes in v5: - Not change arm32 and keep inerrupts_enabled() macro for gicv3 driver. - Move irqentry_state definition into arch/arm64/kernel/entry-common.c. - Avoid removing the __enter_from_*() and __exit_to_*() wrappers. - Update "irqentry_state_t ret/irq_state" to "state" to keep it consistently. - Use generic irq entry header for PREEMPT_DYNAMIC after split the generic entry. - Also refactor the ARM64 syscall code. - Introduce arch_ptrace_report_syscall_entry/exit(), instead of arch_pre/post_report_syscall_entry/exit() to simplify code. - Make the syscall patches clear separation. - Update the commit message. - Link to v4: https://lore.kernel.org/all/20241025100700.3714552-1-ruanjinjie@huawei.com/ Changes in v4: - Rework/cleanup split into a few patches as Mark suggested. - Replace interrupts_enabled() macro with regs_irqs_disabled(), instead of left it here. - Remove rcu and lockdep state in pt_regs by using temporary irqentry_state_t as Mark suggested. - Remove some unnecessary intermediate functions to make it clear. - Rework preempt irq and PREEMPT_DYNAMIC code to make the switch more clear. - arch_prepare_*_entry/exit() -> arch_pre_*_entry/exit(). - Expand the arch functions comment. - Make arch functions closer to its caller. - Declare saved_reg in for block. - Remove arch_exit_to_kernel_mode_prepare(), arch_enter_from_kernel_mode(). - Adjust "Add few arch functions to use generic entry" patch to be the penultimate. - Update the commit message. - Add suggested-by. - Link to v3: https://lore.kernel.org/all/20240629085601.470241-1-ruanjinjie@huawei.com/ Changes in v3: - Test the MTE test cases. - Handle forget_syscall() in arch_post_report_syscall_entry() - Make the arch funcs not use __weak as Thomas suggested, so move the arch funcs to entry-common.h, and make arch_forget_syscall() folded in arch_post_report_syscall_entry() as suggested. - Move report_single_step() to thread_info.h for arm64 - Change __always_inline() to inline, add inline for the other arch funcs. - Remove unused signal.h for entry-common.h. - Add Suggested-by. - Update the commit message. Changes in v2: - Add tested-by. - Fix a bug that not call arch_post_report_syscall_entry() in syscall_trace_enter() if ptrace_report_syscall_entry() return not zero. - Refactor report_syscall(). - Add comment for arch_prepare_report_syscall_exit(). - Adjust entry-common.h header file inclusion to alphabetical order. - Update the commit message. Jinjie Ruan (15): arm64: Remove unused _TIF_WORK_MASK arm64/ptrace: Split report_syscall() arm64/ptrace: Return early for ptrace_report_syscall_entry() error arm64/ptrace: Refactor syscall_trace_enter/exit() arm64: ptrace: Move rseq_syscall() before audit_syscall_exit() arm64: syscall: Rework el0_svc_common() arm64/ptrace: Not check _TIF_SECCOMP/SYSCALL_EMU for syscall_exit_work() arm64/ptrace: Do not report_syscall_exit() for PTRACE_SYSEMU_SINGLESTEP arm64/ptrace: Expand secure_computing() in place arm64/ptrace: Use syscall_get_arguments() helper entry: Split syscall_exit_to_user_mode_work() for arch reuse entry: Add arch_ptrace_report_syscall_entry/exit() arm64: entry: Convert to generic entry arm64: Inline el0_svc_common() entry: Inline syscall_exit_work() kemal (1): selftests: sud_test: Support aarch64 arch/arm64/Kconfig | 2 +- arch/arm64/include/asm/entry-common.h | 76 ++++++++++++++ arch/arm64/include/asm/syscall.h | 19 +++- arch/arm64/include/asm/thread_info.h | 22 +---- arch/arm64/kernel/debug-monitors.c | 7 ++ arch/arm64/kernel/ptrace.c | 94 ------------------ arch/arm64/kernel/signal.c | 2 +- arch/arm64/kernel/syscall.c | 29 ++---- include/linux/entry-common.h | 98 ++++++++++++++++--- kernel/entry/syscall-common.c | 60 +++++------- .../syscall_user_dispatch/sud_test.c | 4 + 11 files changed, 220 insertions(+), 193 deletions(-) -- 2.34.1

1 week, 4 days

[PATCH] kunit: Protect KUNIT_BINARY_STR_ASSERTION against ERR_PTR values

by Richard Fitzgerald

Replace the NULL checks with IS_ERR_OR_NULL() in KUNIT_BINARY_STR_ASSERTION() to prevent the strcmp() faulting if a passed pointer is an ERR_PTR. Commit 7ece381aa72d4 ("kunit: Protect string comparisons against NULL") added the checks for NULL on both pointers so that asserts would fail, instead of faulting, if either pointer is NULL. But either pointer could hold an ERR_PTR value. This assumes that the assertion is expecting both strings to be valid, and is asserting the equality of their _content_. Signed-off-by: Richard Fitzgerald <rf(a)opensource.cirrus.com> --- include/kunit/test.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/kunit/test.h b/include/kunit/test.h index 5ec5182b5e57..9cd1594ab697 100644 --- a/include/kunit/test.h +++ b/include/kunit/test.h @@ -906,7 +906,8 @@ do { \ }; \ \ _KUNIT_SAVE_LOC(test); \ - if (likely((__left) && (__right) && (strcmp(__left, __right) op 0))) \ + if (likely(!IS_ERR_OR_NULL(__left) && !IS_ERR_OR_NULL(__right) && \ + (strcmp(__left, __right) op 0))) \ break; \ \ \ -- 2.47.3

1 week, 5 days

[PATCH v3 0/4] KVM: selftests: arm64: Improve diagnostics from set_id_regs

by Mark Brown

While debugging issues related to aarch64 only systems I ran into speedbumps due to the lack of detail in the results reported when the guest register read and reset value preservation tests were run, they generated an immediately fatal assert without indicating which register was being tested. Update these tests to report a result per register, making it much easier to see what the problem being reported is. A similar, though less severe, issue exists with the validation of the individual bitfields in registers due to the use of immediately fatal asserts. Update those asserts to be standard kselftest reports. Finally we have a fix for spurious errors on some NV systems. Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v3: - Rebase onto v6.19-rc1. - Link to v2: https://patch.msgid.link/20251114-kvm-arm64-set-id-regs-aarch64-v2-0-672f21… Changes in v2: - Add a fix for spurious failures with 64 bit only guests. - Link to v1: https://patch.msgid.link/20251030-kvm-arm64-set-id-regs-aarch64-v1-0-96fe0d… --- Mark Brown (4): KVM: selftests: arm64: Report set_id_reg reads of test registers as tests KVM: selftests: arm64: Report register reset tests individually KVM: selftests: arm64: Make set_id_regs bitfield validatity checks non-fatal KVM: selftests: arm64: Skip all 32 bit IDs when set_id_regs is aarch64 only tools/testing/selftests/kvm/arm64/set_id_regs.c | 150 ++++++++++++++++++------ 1 file changed, 111 insertions(+), 39 deletions(-) --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20251028-kvm-arm64-set-id-regs-aarch64-ebb77969401c Best regards, -- Mark Brown <broonie(a)kernel.org>

1 week, 5 days

[PATCH net-next v9 0/6] Suspend IRQs during application busy periods

by Joe Damato

Greetings: Welcome to v9, see changelog below. This revision addresses feedback Willem gave on the selftests. No functional or code changes to the implementation were made and performance tests were not re-run. This series introduces a new mechanism, IRQ suspension, which allows network applications using epoll to mask IRQs during periods of high traffic while also reducing tail latency (compared to existing mechanisms, see below) during periods of low traffic. In doing so, this balances CPU consumption with network processing efficiency. Martin Karsten (CC'd) and I have been collaborating on this series for several months and have appreciated the feedback from the community on our RFC [1]. We've updated the cover letter and kernel documentation in an attempt to more clearly explain how this mechanism works, how applications can use it, and how it compares to existing mechanisms in the kernel. I briefly mentioned this idea at netdev conf 2024 (for those who were there) and Martin described this idea in an earlier paper presented at Sigmetrics 2024 [2]. ~ The short explanation (TL;DR) We propose adding a new napi config parameter: irq_suspend_timeout to help balance CPU usage and network processing efficiency when using IRQ deferral and napi busy poll. If this parameter is set to a non-zero value *and* a user application has enabled preferred busy poll on a busy poll context (via the EPIOCSPARAMS ioctl introduced in commit 18e2bf0edf4d ("eventpoll: Add epoll ioctl for epoll_params")), then application calls to epoll_wait for that context will cause device IRQs and softirq processing to be suspended as long as epoll_wait successfully retrieves data from the NAPI. Each time data is retrieved, the irq_suspend_timeout is deferred. If/when network traffic subsides and epoll_wait returns no data, IRQ suspension is immediately reverted back to the existing napi_defer_hard_irqs and gro_flush_timeout mechanism which was introduced in commit 6f8b12d661d0 ("net: napi: add hard irqs deferral feature")). The irq_suspend_timeout serves as a safety mechanism. If userland takes a long time processing data, irq_suspend_timeout will fire and restart normal NAPI processing. For a more in depth explanation, please continue reading. ~ Comparison with existing mechanisms Interrupt mitigation can be accomplished in napi software, by setting napi_defer_hard_irqs and gro_flush_timeout, or via interrupt coalescing in the NIC. This can be quite efficient, but in both cases, a fixed timeout (or packet count) needs to be configured. However, a fixed timeout cannot effectively support both low- and high-load situations: At low load, an application typically processes a few requests and then waits to receive more input data. In this scenario, a large timeout will cause unnecessary latency. At high load, an application typically processes many requests before being ready to receive more input data. In this case, a small timeout will likely fire prematurely and trigger irq/softirq processing, which interferes with the application's execution. This causes overhead, most likely due to cache contention. While NICs attempt to provide adaptive interrupt coalescing schemes, these cannot properly take into account application-level processing. An alternative packet delivery mechanism is busy-polling, which results in perfect alignment of application processing and network polling. It delivers optimal performance (throughput and latency), but results in 100% cpu utilization and is thus inefficient for below-capacity workloads. We propose to add a new packet delivery mode that properly alternates between busy polling and interrupt-based delivery depending on busy and idle periods of the application. During a busy period, the system operates in busy-polling mode, which avoids interference. During an idle period, the system falls back to interrupt deferral, but with a small timeout to avoid excessive latencies. This delivery mode can also be viewed as an extension of basic interrupt deferral, but alternating between a small and a very large timeout. This delivery mode is efficient, because it avoids softirq execution interfering with application processing during busy periods. It can be used with blocking epoll_wait to conserve cpu cycles during idle periods. The effect of alternating between busy and idle periods is that performance (throughput and latency) is very close to full busy polling, while cpu utilization is lower and very close to interrupt mitigation. ~ Usage details IRQ suspension is introduced via a per-NAPI configuration parameter that controls the maximum time that IRQs can be suspended. Here's how it is intended to work: - The user application (or system administrator) uses the netdev-genl netlink interface to set the pre-existing napi_defer_hard_irqs and gro_flush_timeout NAPI config parameters to enable IRQ deferral. - The user application (or system administrator) sets the proposed irq_suspend_timeout parameter via the netdev-genl netlink interface to a larger value than gro_flush_timeout to enable IRQ suspension. - The user application issues the existing epoll ioctl to set the prefer_busy_poll flag on the epoll context. - The user application then calls epoll_wait to busy poll for network events, as it normally would. - If epoll_wait returns events to userland, IRQs are suspended for the duration of irq_suspend_timeout. - If epoll_wait finds no events and the thread is about to go to sleep, IRQ handling using napi_defer_hard_irqs and gro_flush_timeout is resumed. As long as epoll_wait is retrieving events, IRQs (and softirq processing) for the NAPI being polled remain disabled. When network traffic reduces, eventually a busy poll loop in the kernel will retrieve no data. When this occurs, regular IRQ deferral using gro_flush_timeout for the polled NAPI is re-enabled. Unless IRQ suspension is continued by subsequent calls to epoll_wait, it automatically times out after the irq_suspend_timeout timer expires. Regular deferral is also immediately re-enabled when the epoll context is destroyed. ~ Usage scenario The target scenario for IRQ suspension as packet delivery mode is a system that runs a dominant application with substantial network I/O. The target application can be configured to receive input data up to a certain batch size (via epoll_wait maxevents parameter) and this batch size determines the worst-case latency that application requests might experience. Because packet delivery is suspended during the target application's processing, the batch size also determines the worst-case latency of concurrent applications using the same RX queue(s). gro_flush_timeout should be set as small as possible, but large enough to make sure that a single request is likely not being interfered with. irq_suspend_timeout is largely a safety mechanism against misbehaving applications. It should be set large enough to cover the processing of an entire application batch, i.e., the factor between gro_flush_timeout and irq_suspend_timeout should roughly correspond to the maximum batch size that the target application would process in one go. ~ Important call out in the implementation - Enabling per epoll-context preferred busy poll will now effectively lead to a nonblocking iteration through napi_busy_loop, even when busy_poll_usecs is 0. See patch 4. ~ Benchmark configs & descriptions The changes were benchmarked with memcached [3] using the benchmarking tool mutilate [4]. To facilitate benchmarking, a small patch [5] was applied to memcached 1.6.29 to allow setting per-epoll context preferred busy poll and other settings via environment variables. Another small patch [6] was applied to libevent to enable full busy-polling. Multiple scenarios were benchmarked as described below and the scripts used for producing these results can be found on github [7] (note: all scenarios use NAPI-based traffic splitting via SO_INCOMING_ID by passing -N to memcached): - base: - no other options enabled - deferX: - set defer_hard_irqs to 100 - set gro_flush_timeout to X,000 - napibusy: - set defer_hard_irqs to 100 - set gro_flush_timeout to 200,000 - enable busy poll via the existing ioctl (busy_poll_usecs = 64, busy_poll_budget = 64, prefer_busy_poll = true) - fullbusy: - set defer_hard_irqs to 100 - set gro_flush_timeout to 5,000,000 - enable busy poll via the existing ioctl (busy_poll_usecs = 1000, busy_poll_budget = 64, prefer_busy_poll = true) - change memcached's nonblocking epoll_wait invocation (via libevent) to using a 1 ms timeout - suspend0: - set defer_hard_irqs to 0 - set gro_flush_timeout to 0 - set irq_suspend_timeout to 20,000,000 - enable busy poll via the existing ioctl (busy_poll_usecs = 0, busy_poll_budget = 64, prefer_busy_poll = true) - suspendX: - set defer_hard_irqs to 100 - set gro_flush_timeout to X,000 - set irq_suspend_timeout to 20,000,000 - enable busy poll via the existing ioctl (busy_poll_usecs = 0, busy_poll_budget = 64, prefer_busy_poll = true) ~ Benchmark results Tested on: Single socket AMD EPYC 7662 64-Core Processor Hyperthreading disabled 4 NUMA Zones (NPS=4) 16 CPUs per NUMA zone (64 cores total) 2 x Dual port 100gbps Mellanox Technologies ConnectX-5 Ex EN NIC The test machine is configured such that a single interface has 8 RX queues. The queues' IRQs and memcached are pinned to CPUs that are NUMA-local to the interface which is under test. The NIC's interrupt coalescing configuration is left at boot-time defaults. Results: Results are shown below. The mechanism added by this series is represented by the 'suspend' cases. Data presented shows a summary over nearly 10 runs of each test case [8] using the scripts on github [7]. For latency, the median is shown. For throughput and CPU utilization, the average is shown. The results also include cycles-per-query (cpq) and instruction-per-query (ipq) metrics, following the methodology proposed in [2], to augment the CPU utilization numbers, which could be skewed due to frequency scaling. We find that this does not appear to be the case as CPU utilization and low-level metrics show similar trends. These results were captured using the scripts on github [7] to illustrate how this approach compares with other pre-existing mechanisms. This data is not to be interpreted as scientific data captured in a fully isolated lab setting, but instead as best effort, illustrative information comparing and contrasting tradeoffs. The absolute QPS results shift between submissions, but the relative differences are equivalent. As patches are rebased, several factors likely influence overall performance. Compare: - Throughput (MAX) and latencies of base vs suspend. - CPU usage of napibusy and fullbusy during lower load (200K, 400K for example) vs suspend. - Latency of the defer variants vs suspend as timeout and load increases. - suspend0, which sets defer_hard_irqs and gro_flush_timeout to 0, has nearly the same performance as the base case (this is FAQ item #1). The overall takeaway is that the suspend variants provide a superior combination of high throughput, low latency, and low cpu utilization compared to all other variants. Each of the suspend variants works very well, but some fine-tuning between latency and cpu utilization is still possible by tuning the small timeout (gro_flush_timeout). Note: we've reorganized the results to make comparison among testcases with the same load easier. testcase load qps avglat 95%lat 99%lat cpu cpq ipq base 200K 199946 112 239 416 26 12973 11343 defer10 200K 199971 54 124 142 29 19412 17460 defer20 200K 199986 60 130 153 26 15644 14095 defer50 200K 200025 79 144 182 23 12122 11632 defer200 200K 199999 164 254 309 19 8923 9635 fullbusy 200K 199998 46 118 133 100 43658 23133 napibusy 200K 199983 100 237 277 56 24840 24716 suspend0 200K 200020 105 249 432 30 14264 11796 suspend10 200K 199950 53 123 141 32 19518 16903 suspend20 200K 200037 58 126 151 30 16426 14736 suspend50 200K 199961 73 136 177 26 13310 12633 suspend200 200K 199998 149 251 306 21 9566 10203 testcase load qps avglat 95%lat 99%lat cpu cpq ipq base 400K 400014 139 269 707 41 9476 9343 defer10 400K 400016 59 133 166 53 13991 12989 defer20 400K 399952 67 140 172 47 12063 11644 defer50 400K 400007 87 162 198 39 9384 9880 defer200 400K 399979 181 274 330 31 7089 8430 fullbusy 400K 399987 50 123 156 100 21827 16037 napibusy 400K 400014 76 222 272 83 18185 16529 suspend0 400K 400015 127 350 776 47 10699 9603 suspend10 400K 400023 57 129 164 54 13758 13178 suspend20 400K 400043 62 135 169 49 12071 11826 suspend50 400K 400071 76 149 186 42 10011 10301 suspend200 400K 399961 154 269 327 34 7827 8774 testcase load qps avglat 95%lat 99%lat cpu cpq ipq base 600K 599951 149 266 574 61 9265 8876 defer10 600K 600006 71 147 203 76 11866 10936 defer20 600K 600123 76 152 203 66 10430 10342 defer50 600K 600162 95 172 217 54 8526 9142 defer200 600K 599942 200 301 357 46 6977 8212 fullbusy 600K 599990 55 127 177 100 14551 13983 napibusy 600K 600035 63 160 250 96 13937 14140 suspend0 600K 599903 127 320 732 68 10166 8963 suspend10 600K 599908 63 137 192 69 10902 11100 suspend20 600K 599961 66 141 194 65 9976 10370 suspend50 600K 599973 80 159 204 57 8678 9381 suspend200 600K 600010 157 277 346 48 7133 8381 testcase load qps avglat 95%lat 99%lat cpu cpq ipq base 800K 800039 181 300 536 87 9585 8304 defer10 800K 800038 181 530 939 96 10564 8970 defer20 800K 800029 112 225 329 90 10056 8935 defer50 800K 799999 120 208 296 82 9234 8562 defer200 800K 800066 227 338 401 63 7117 8129 fullbusy 800K 800040 61 134 190 100 10913 12608 napibusy 800K 799944 64 141 214 99 10828 12588 suspend0 800K 799911 126 248 509 85 9346 8498 suspend10 800K 800006 69 143 200 83 9410 9845 suspend20 800K 800120 74 150 207 78 8786 9454 suspend50 800K 799989 87 168 224 71 7946 8833 suspend200 800K 799987 160 292 357 62 6923 8229 testcase load qps avglat 95%lat 99%lat cpu cpq ipq base 1000K 906879 4079 5751 6216 98 9496 7904 defer10 1000K 860849 3643 6274 6730 99 10040 8676 defer20 1000K 896063 3298 5840 6349 98 9620 8237 defer50 1000K 919782 2962 5513 5807 97 9284 7951 defer200 1000K 970941 3059 5348 5984 95 8593 7959 fullbusy 1000K 999950 70 150 207 100 8732 10777 napibusy 1000K 999996 78 154 223 100 8722 10656 suspend0 1000K 949706 2666 5770 6660 99 9071 8046 suspend10 1000K 1000024 80 160 220 92 8137 9035 suspend20 1000K 1000059 83 165 226 89 7850 8804 suspend50 1000K 999955 95 180 240 84 7411 8459 suspend200 1000K 999914 163 299 366 77 6833 8078 testcase load qps avglat 95%lat 99%lat cpu cpq ipq base MAX 1037654 4184 5453 5810 100 8411 7938 defer10 MAX 905607 4840 6151 6380 100 9639 8431 defer20 MAX 986463 4455 5594 5796 100 8848 8110 defer50 MAX 1077030 4000 5073 5299 100 8104 7920 defer200 MAX 1040728 4152 5385 5765 100 8379 7849 fullbusy MAX 1247536 3518 3935 3984 100 6998 7930 napibusy MAX 1136310 3799 7756 9964 100 7670 7877 suspend0 MAX 1057509 4132 5724 6185 100 8253 7918 suspend10 MAX 1215147 3580 3957 4041 100 7185 7944 suspend20 MAX 1216469 3576 3953 3988 100 7175 7950 suspend50 MAX 1215871 3577 3961 4075 100 7181 7949 suspend200 MAX 1216882 3556 3951 3988 100 7175 7955 ~ FAQ - Why is a new parameter needed? Does irq_suspend_timeout override gro_flush_timeout? Using the suspend mechanism causes the system to alternate between polling mode and irq-driven packet delivery. During busy periods, irq_suspend_timeout overrides gro_flush_timeout and keeps the system busy polling, but when epoll finds no events, the setting of gro_flush_timeout and napi_defer_hard_irqs determine the next step. There are essentially three possible loops for network processing and packet delivery: 1) hardirq -> softirq -> napi poll; basic interrupt delivery 2) timer -> softirq -> napi poll; deferred irq processing 3) epoll -> busy-poll -> napi poll; busy looping Loop 2 can take control from Loop 1, if gro_flush_timeout and napi_defer_hard_irqs are set. If gro_flush_timeout and napi_defer_hard_irqs are set, Loops 2 and 3 "wrestle" with each other for control. During busy periods, irq_suspend_timeout is used as timer in Loop 2, which essentially tilts this in favour of Loop 3. If gro_flush_timeout and napi_defer_hard_irqs are not set, Loop 3 cannot take control from Loop 1. Therefore, setting gro_flush_timeout and napi_defer_hard_irqs is the recommended usage, because otherwise setting irq_suspend_timeout might not have any discernible effect. This is shown in the results above: compare suspend0 with the base case. Note that the lack of napi_defer_hard_irqs and gro_flush_timeout produce similar results for both, which encourages the use of napi_defer_hard_irqs and gro_flush_timeout in addition to irq_suspend_timeout. - Can the new timeout value be threaded through the new epoll ioctl ? It is possible, but presents challenges for userspace. User applications must ensure that the file descriptors added to epoll contexts have the same NAPI ID to support busy polling. An epoll context is not permanently tied to any particular NAPI ID. So, a user application could decide to clear the file descriptors from the context and add a new set of file descriptors with a different NAPI ID to the context. Busy polling would work as expected, but the meaning of the suspend timeout becomes ambiguous because IRQs are not inherently associated with epoll contexts, but rather with the NAPI. The user program would need to reissue the ioctl to set the irq_suspend_timeout, but the napi_defer_hard_irqs and gro_flush_timeout settings would come from the NAPI's napi_config (which are set either by sysfs or by netlink). Such an interface seems awkard to use from a user perspective. Further, IRQs are related to NAPIs, which is why they are stored in the napi_config space. Putting the irq_suspend_timeout in the epoll context while other IRQ deferral mechanisms remain in the NAPI's napi_config space seems like an odd design choice. We've opted to keep all of the IRQ deferral parameters together and place the irq_suspend_timeout in napi_config. This has nice benefits for userspace: if a user app were to remove all file descriptors from an epoll context and add new file descriptors with a new NAPI ID, the correct suspend timeout for that NAPI ID would be used automatically without the user application needing to do anything (like re-issuing an ioctl, for example). All IRQ deferral related parameters are in one place and can all be set the same way: with netlink. - Can irq suspend be built by combining NIC coalescing and gro_flush_timeout ? No. The problem is that the long timeout must engage if and only if prefer-busy is active. When using NIC coalescing for the short timeout (without napi_defer_hard_irqs/gro_flush_timeout), an interrupt after an idle period will trigger softirq, which will run napi polling. At this point, prefer-busy is not active, so NIC interrupts would be re-enabled. Then it is not possible for the longer timeout to interject to switch control back to polling. In other words, only by using the software timer for the short timeout, it is possible to extend the timeout without having to reprogram the NIC timer or reach down directly and disable interrupts. Using gro_flush_timeout for the long timeout also has problems, for the same underlying reason. In the current napi implementation, gro_flush_timeout is not tied to prefer-busy. We'd either have to change that and in the process modify the existing deferral mechanism, or introduce a state variable to determine whether gro_flush_timeout is used as long timeout for irq suspend or whether it is used for its default purpose. In an earlier version, we did try something similar to the latter and made it work, but it ends up being a lot more convoluted than our current proposal. - Isn't it already possible to combine busy looping with irq deferral? Yes, in fact enabling irq deferral via napi_defer_hard_irqs and gro_flush_timeout is a precondition for prefer_busy_poll to have an effect. If the application also uses a tight busy loop with essentially nonblocking epoll_wait (accomplished with a very short timeout parameter), this is the fullbusy case shown in the results. An application using blocking epoll_wait is shown as the napibusy case in the results. It's a hybrid approach that provides limited latency benefits compared to the base case and plain irq deferral, but not as good as fullbusy or suspend. ~ Special thanks Several people were involved in earlier stages of the development of this mechanism whom we'd like to thank: - Peter Cai (CC'd), for the initial kernel patch and his contributions to the paper. - Mohammadamin Shafie (CC'd), for testing various versions of the kernel patch and providing helpful feedback. Thanks, Martin and Joe [1]: https://lore.kernel.org/netdev/20240812125717.413108-1-jdamato@fastly.com/ [2]: https://doi.org/10.1145/3626780 [3]: https://github.com/memcached/memcached/blob/master/doc/napi_ids.txt [4]: https://github.com/leverich/mutilate [5]: https://raw.githubusercontent.com/martinkarsten/irqsuspend/main/patches/mem… [6]: https://raw.githubusercontent.com/martinkarsten/irqsuspend/main/patches/lib… [7]: https://github.com/martinkarsten/irqsuspend [8]: https://github.com/martinkarsten/irqsuspend/tree/main/results v9: - Addresses Willem's feedback on the selftests in patch 5 by fixing the SPDX-License-Identifier, moving constants into variables in the test script, reducing code duplication, shortening long lines, and renaming variables to be more reader friendly. In the C test file, added a comment explaining the if def blob and changed a few types for strtoul. v8: https://lore.kernel.org/netdev/20241108045337.292905-1-jdamato@fastly.com/ - Update patch 2 to drop the exports, as requested by Jakub. v7: https://lore.kernel.org/netdev/20241108023912.98416-1-jdamato@fastly.com/ - Jakub noted that patch 2 adds unnecessary complexity by checking the suspend timeout in the NAPI loop. This makes the code more complicated and difficult to reason about. He's right; we've dropped patch 2 which simplifies this series. - Updated the cover letter with a full re-run of all test cases. - Updated FAQ #2. v6: https://lore.kernel.org/netdev/20241104215542.215919-1-jdamato@fastly.com/ - Updated the cover letter with a full re-run of all test cases, including a new case suspend0, as requested by Sridhar previously. - Updated the kernel documentation in patch 7 as suggested by Bagas Sanjaya, which improved the htmldoc output. v5: https://lore.kernel.org/netdev/20241103052421.518856-1-jdamato@fastly.com/ - Adjusted patch 5 to only suspend IRQs when ep_send_events returns a positive return value. This issue was pointed out by Hillf Danton. - Updated the commit message of patch 6 which still mentioned netcat, despite the code being updated in v4 to replace it with socat and fixed misspelling of netdevsim. - Fixed a minor typo in patch 7 and removed an unnecessary paragraph. - Added Sridhar Samudrala's Reviewed-by to patch 1-5 and 7. v4: https://lore.kernel.org/netdev/20241102005214.32443-1-jdamato@fastly.com/ - Added a new FAQ item to cover letter. - Updated patch 6 to use socat instead of nc in busy_poll_test.sh and updated busy_poller.c to use netlink directly to configure napi params. - Updated the kernel documentation in patch 7 to include more details. - Dropped Stanislav's Acked-by and Bagas' Reviewed-by from patch 7 since the documentation was updated. v3: https://lore.kernel.org/netdev/20241101004846.32532-1-jdamato@fastly.com/ - Added Stanislav Fomichev's Acked-by to every patch except the newly added selftest. - Added Bagas Sanjaya's Reviewed-by to the documentation patch. - Fixed the commit message of patch 2 to remove a reference to the now non-existent sysfs setting. - Added a self test which tests both "regular" busy poll and busy poll with suspend enabled. This was added as patch 6 as requested by Paolo. netdevsim was chosen instead of veth due to netdevsim's pre-existing support for netdev-genl. See the commit message of patch 6 for more details. v2: https://lore.kernel.org/bpf/20241021015311.95468-1-jdamato@fastly.com/ - Cover letter updated, including a re-run of test data. - Patch 1 rewritten to use netdev-genl instead of sysfs. - Patch 3 updated with a comment added to napi_resume_irqs. - Patch 4 rebased to apply now that commit b9ca079dd6b0 ("eventpoll: Annotate data-race of busy_poll_usecs") has been picked up from VFS. - Patch 6 updated the kernel documentation. rfc -> v1: - Cover letter updated to include more details. - Patch 1 updated to remove the documentation added. This was moved to patch 6 with the rest of the docs (see below). - Patch 5 updated to fix an error uncovered by the kernel build robot. See patch 5's changelog for more details. - Patch 6 added which updates kernel documentation. Joe Damato (2): selftests: net: Add busy_poll_test docs: networking: Describe irq suspension Martin Karsten (4): net: Add napi_struct parameter irq_suspend_timeout net: Add control functions for irq suspension eventpoll: Trigger napi_busy_loop, if prefer_busy_poll is set eventpoll: Control irq suspension for prefer_busy_poll Documentation/netlink/specs/netdev.yaml | 7 + Documentation/networking/napi.rst | 170 ++++++++- fs/eventpoll.c | 36 +- include/linux/netdevice.h | 2 + include/net/busy_poll.h | 3 + include/uapi/linux/netdev.h | 1 + net/core/dev.c | 39 ++ net/core/dev.h | 25 ++ net/core/netdev-genl-gen.c | 5 +- net/core/netdev-genl.c | 12 + tools/include/uapi/linux/netdev.h | 1 + tools/testing/selftests/net/.gitignore | 1 + tools/testing/selftests/net/Makefile | 3 +- tools/testing/selftests/net/busy_poll_test.sh | 165 +++++++++ tools/testing/selftests/net/busy_poller.c | 346 ++++++++++++++++++ 15 files changed, 809 insertions(+), 7 deletions(-) create mode 100755 tools/testing/selftests/net/busy_poll_test.sh create mode 100644 tools/testing/selftests/net/busy_poller.c base-commit: dc7c381bb8649e3701ed64f6c3e55316675904d7 -- 2.25.1

1 week, 5 days

[PATCH 0/3] HID: multitouch: set INPUT_PROP_PRESSUREPAD on compatible touchpads

by Peter Hutterer

Note: this requires INPUT_PROP_PRESSUREPAD [1] which is not yet available in Linus' tree but it is in Dmitry's for-linus tree. Nicely enough MS defines a button type for a pressurepad touchpad [2] and it looks like most touchpad vendors fill this in. The selftests require a bit of prep work (and a hack for the test itself) - hidtools 0.12 requires python-libevdev 0.13 which in turn provides constructors for unknown properties. [1] https://lore.kernel.org/linux-input/20251030011735.GA969565@quokka/T/#m9d9b… [2] https://learn.microsoft.com/en-us/windows-hardware/design/component-guideli… Signed-off-by: Peter Hutterer <peter.hutterer(a)who-t.net> --- Peter Hutterer (3): selftests/hid: require hidtools 0.12 selftests/hid: use a enum class for the different button types HID: multitouch: set INPUT_PROP_PRESSUREPAD based on Digitizer/Button Type drivers/hid/hid-multitouch.c | 12 ++++- tools/testing/selftests/hid/tests/conftest.py | 14 +++++ .../testing/selftests/hid/tests/test_multitouch.py | 61 +++++++++++++++++----- 3 files changed, 73 insertions(+), 14 deletions(-) --- base-commit: 2bc4c50a42f8b83f611d0475598dc72740e87640 change-id: 20251111-wip-hid-pressurepad-8a800cdf1813 Best regards, -- Peter Hutterer <peter.hutterer(a)who-t.net>

1 week, 5 days

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