Linux-kselftest-mirror May 2025

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[PATCH v5 0/4] mm: introduce THP deferred setting

by Nico Pache

This series is a follow-up to [1], which adds mTHP support to khugepaged. mTHP khugepaged support is a "loose" dependency for the sysfs/sysctl configs to make sense. Without it global="defer" and mTHP="inherit" case is "undefined" behavior. We've seen cases were customers switching from RHEL7 to RHEL8 see a significant increase in the memory footprint for the same workloads. Through our investigations we found that a large contributing factor to the increase in RSS was an increase in THP usage. For workloads like MySQL, or when using allocators like jemalloc, it is often recommended to set /transparent_hugepages/enabled=never. This is in part due to performance degradations and increased memory waste. This series introduces enabled=defer, this setting acts as a middle ground between always and madvise. If the mapping is MADV_HUGEPAGE, the page fault handler will act normally, making a hugepage if possible. If the allocation is not MADV_HUGEPAGE, then the page fault handler will default to the base size allocation. The caveat is that khugepaged can still operate on pages that are not MADV_HUGEPAGE. This allows for three things... one, applications specifically designed to use hugepages will get them, and two, applications that don't use hugepages can still benefit from them without aggressively inserting THPs at every possible chance. This curbs the memory waste, and defers the use of hugepages to khugepaged. Khugepaged can then scan the memory for eligible collapsing. Lastly there is the added benefit for those who want THPs but experience higher latency PFs. Now you can get base page performance at the PF handler and Hugepage performance for those mappings after they collapse. Admins may want to lower max_ptes_none, if not, khugepaged may aggressively collapse single allocations into hugepages. TESTING: - Built for x86_64, aarch64, ppc64le, and s390x - selftests mm - In [1] I provided a script [2] that has multiple access patterns - lots of general use. - redis testing. This test was my original case for the defer mode. What I was able to prove was that THP=always leads to increased max_latency cases; hence why it is recommended to disable THPs for redis servers. However with 'defer' we dont have the max_latency spikes and can still get the system to utilize THPs. I further tested this with the mTHP defer setting and found that redis (and probably other jmalloc users) can utilize THPs via defer (+mTHP defer) without a large latency penalty and some potential gains. I uploaded some mmtest results here[3] which compares: stock+thp=never stock+(m)thp=always khugepaged-mthp + defer (max_ptes_none=64) The results show that (m)THPs can cause some throughput regression in some cases, but also has gains in other cases. The mTHP+defer results have more gains and less losses over the (m)THP=always case. V5 Changes: - rebased dependent series - added reviewed-by tag on 2/4 V4 Changes: - Minor Documentation fixes - rebased the dependent series [1] onto mm-unstable commit 0e68b850b1d3 ("vmalloc: use atomic_long_add_return_relaxed()") V3 Changes: - Combined the documentation commits into one, and moved a section to the khugepaged mthp patchset V2 Changes: - base changes on mTHP khugepaged support - Fix selftests parsing issue - add mTHP defer option - add mTHP defer Documentation [1] - https://lore.kernel.org/lkml/20250428181218.85925-1-npache@redhat.com/ [2] - https://gitlab.com/npache/khugepaged_mthp_test [3] - https://people.redhat.com/npache/mthp_khugepaged_defer/testoutput2/output.h… Nico Pache (4): mm: defer THP insertion to khugepaged mm: document (m)THP defer usage khugepaged: add defer option to mTHP options selftests: mm: add defer to thp setting parser Documentation/admin-guide/mm/transhuge.rst | 31 +++++++--- include/linux/huge_mm.h | 18 +++++- mm/huge_memory.c | 69 +++++++++++++++++++--- mm/khugepaged.c | 8 +-- tools/testing/selftests/mm/thp_settings.c | 1 + tools/testing/selftests/mm/thp_settings.h | 1 + 6 files changed, 106 insertions(+), 22 deletions(-) -- 2.48.1

1 month, 1 week

[PATCH bpf-next v3 0/2] bpf: Allow XDP_REDIRECT for XDP dev-bound programs

by Lorenzo Bianconi

In the current implementation if the program is dev-bound to a specific device, it will not be possible to perform XDP_REDIRECT into a DEVMAP or CPUMAP even if the program is running in the driver NAPI context. Fix the issue introducing __bpf_prog_map_compatible utility routine in order to avoid bpf_prog_is_dev_bound() during the XDP program load. Continue forbidding to attach a dev-bound program to XDP maps. --- Changes in v3: - move seltest changes in a dedicated patch - Link to v2: https://lore.kernel.org/r/20250423-xdp-prog-bound-fix-v2-1-51742a5dfbce@ker… Changes in v2: - Introduce __bpf_prog_map_compatible() utility routine in order to skip bpf_prog_is_dev_bound check in bpf_check_tail_call() - Extend xdp_metadata selftest - Link to v1: https://lore.kernel.org/r/20250422-xdp-prog-bound-fix-v1-1-0b581fa186fe@ker… --- Lorenzo Bianconi (2): bpf: Allow XDP dev-bound programs to perform XDP_REDIRECT into maps selftests/bpf: xdp_metadata: check XDP_REDIRCT support for dev-bound progs kernel/bpf/core.c | 27 +++++++++++++--------- .../selftests/bpf/prog_tests/xdp_metadata.c | 22 +++++++++++++++++- tools/testing/selftests/bpf/progs/xdp_metadata.c | 13 +++++++++++ 3 files changed, 50 insertions(+), 12 deletions(-) --- base-commit: 91dbac4076537b464639953c055c460d2bdfc7ea change-id: 20250422-xdp-prog-bound-fix-9f30f3e134aa Best regards, -- Lorenzo Bianconi <lorenzo(a)kernel.org>

1 month, 1 week

[PATCH 0/5] riscv: misaligned: fix interruptible context and add tests

by Clément Léger

This series fixes misaligned access handling when in non interruptible context by reenabling interrupts when possible. A previous commit changed raw_copy_from_user() with copy_from_user() which enables page faulting and thus can sleep. While correct, a warning is now triggered due to being called in an invalid context (sleeping in non-interruptible). This series fixes that problem by factorizing misaligned load/store entry in a single function than reenables interrupt if the interrupted context had interrupts enabled. In order for misaligned handling problems to be caught sooner, add a kselftest for all the currently supported instructions . Note: these commits were actually part of another larger series for misaligned request delegation but was split since it isn't directly required. Clément Léger (5): riscv: misaligned: factorize trap handling riscv: misaligned: enable IRQs while handling misaligned accesses riscv: misaligned: use get_user() instead of __get_user() Documentation/sysctl: add riscv to unaligned-trap supported archs selftests: riscv: add misaligned access testing Documentation/admin-guide/sysctl/kernel.rst | 4 +- arch/riscv/kernel/traps.c | 57 ++-- arch/riscv/kernel/traps_misaligned.c | 2 +- .../selftests/riscv/misaligned/.gitignore | 1 + .../selftests/riscv/misaligned/Makefile | 12 + .../selftests/riscv/misaligned/common.S | 33 +++ .../testing/selftests/riscv/misaligned/fpu.S | 180 +++++++++++++ tools/testing/selftests/riscv/misaligned/gp.S | 103 +++++++ .../selftests/riscv/misaligned/misaligned.c | 254 ++++++++++++++++++ 9 files changed, 614 insertions(+), 32 deletions(-) create mode 100644 tools/testing/selftests/riscv/misaligned/.gitignore create mode 100644 tools/testing/selftests/riscv/misaligned/Makefile create mode 100644 tools/testing/selftests/riscv/misaligned/common.S create mode 100644 tools/testing/selftests/riscv/misaligned/fpu.S create mode 100644 tools/testing/selftests/riscv/misaligned/gp.S create mode 100644 tools/testing/selftests/riscv/misaligned/misaligned.c -- 2.49.0

1 month, 1 week

[RFC net-next v1 1/2] udp: Introduce UDP_STOP_RCV option for UDP

by Jiayuan Chen

For some services we are using "established-over-unconnected" model. ''' // create unconnected socket and 'listen()' srv_fd = socket(AF_INET, SOCK_DGRAM) setsockopt(srv_fd, SO_REUSEPORT) bind(srv_fd, SERVER_ADDR, SERVER_PORT) // 'accept()' data, client_addr = recvmsg(srv_fd) // create a connected socket for this request cli_fd = socket(AF_INET, SOCK_DGRAM) setsockopt(cli_fd, SO_REUSEPORT) bind(cli_fd, SERVER_ADDR, SERVER_PORT) connect(cli, client_addr) ... // do handshake with cli_fd ''' This programming pattern simulates accept() using UDP, creating a new socket for each client request. The server can then use separate sockets to handle client requests, avoiding the need to use a single UDP socket for I/O transmission. But there is a race condition between the bind() and connect() of the connected socket: We might receive unexpected packets belonging to the unconnected socket before connect() is executed, which is not what we need. (Of course, before connect(), the unconnected socket will also receive packets from the connected socket, which is easily resolved because upper-layer protocols typically require explicit boundaries, and we receive a complete packet before creating a connected socket.) Before this patch, the connected socket had to filter requests at recvmsg time, acting as a dispatcher to some extent. With this patch, we can consider the bind and connect operations to be atomic. Signed-off-by: Jiayuan Chen <jiayuan.chen(a)linux.dev> --- include/linux/udp.h | 1 + include/uapi/linux/udp.h | 1 + net/ipv4/udp.c | 13 ++++++++++--- net/ipv6/udp.c | 5 +++-- 4 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/linux/udp.h b/include/linux/udp.h index 895240177f4f..8d281a0c0d9d 100644 --- a/include/linux/udp.h +++ b/include/linux/udp.h @@ -42,6 +42,7 @@ enum { UDP_FLAGS_ENCAP_ENABLED, /* This socket enabled encap */ UDP_FLAGS_UDPLITE_SEND_CC, /* set via udplite setsockopt */ UDP_FLAGS_UDPLITE_RECV_CC, /* set via udplite setsockopt */ + UDP_FLAGS_STOP_RCV, /* Stop receiving packets */ }; struct udp_sock { diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h index edca3e430305..bb8e0a749a55 100644 --- a/include/uapi/linux/udp.h +++ b/include/uapi/linux/udp.h @@ -34,6 +34,7 @@ struct udphdr { #define UDP_NO_CHECK6_RX 102 /* Disable accepting checksum for UDP6 */ #define UDP_SEGMENT 103 /* Set GSO segmentation size */ #define UDP_GRO 104 /* This socket can receive UDP GRO packets */ +#define UDP_STOP_RCV 105 /* This socket will not receive any packets */ /* UDP encapsulation types */ #define UDP_ENCAP_ESPINUDP_NON_IKE 1 /* unused draft-ietf-ipsec-nat-t-ike-00/01 */ diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index f9f5b92cf4b6..764d337ab1b3 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -376,7 +376,8 @@ static int compute_score(struct sock *sk, const struct net *net, if (!net_eq(sock_net(sk), net) || udp_sk(sk)->udp_port_hash != hnum || - ipv6_only_sock(sk)) + ipv6_only_sock(sk) || + udp_test_bit(STOP_RCV, sk)) return -1; if (sk->sk_rcv_saddr != daddr) @@ -494,7 +495,7 @@ static struct sock *udp4_lib_lookup2(const struct net *net, result = inet_lookup_reuseport(net, sk, skb, sizeof(struct udphdr), saddr, sport, daddr, hnum, udp_ehashfn); - if (!result) { + if (!result || udp_test_bit(STOP_RCV, result)) { result = sk; continue; } @@ -3031,7 +3032,9 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname, set_xfrm_gro_udp_encap_rcv(up->encap_type, sk->sk_family, sk); sockopt_release_sock(sk); break; - + case UDP_STOP_RCV: + udp_assign_bit(STOP_RCV, sk, valbool); + break; /* * UDP-Lite's partial checksum coverage (RFC 3828). */ @@ -3120,6 +3123,10 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname, val = udp_test_bit(GRO_ENABLED, sk); break; + case UDP_STOP_RCV: + val = udp_test_bit(STOP_RCV, sk); + break; + /* The following two cannot be changed on UDP sockets, the return is * always 0 (which corresponds to the full checksum coverage of UDP). */ case UDPLITE_SEND_CSCOV: diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 7317f8e053f1..55896a78e94b 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -137,7 +137,8 @@ static int compute_score(struct sock *sk, const struct net *net, if (!net_eq(sock_net(sk), net) || udp_sk(sk)->udp_port_hash != hnum || - sk->sk_family != PF_INET6) + sk->sk_family != PF_INET6 || + udp_test_bit(STOP_RCV, sk)) return -1; if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr)) @@ -245,7 +246,7 @@ static struct sock *udp6_lib_lookup2(const struct net *net, result = inet6_lookup_reuseport(net, sk, skb, sizeof(struct udphdr), saddr, sport, daddr, hnum, udp6_ehashfn); - if (!result) { + if (!result || udp_test_bit(STOP_RCV, result)) { result = sk; continue; } -- 2.47.1

1 month, 1 week

[PATCH v3 0/3] RISC-V KVM selftests improvements

by Atish Patra

This series improves the following tests. 1. Get-reg-list : Adds vector support 2. SBI PMU test : Distinguish between different types of illegal exception The first patch is just helper patch that adds stval support during exception handling. Signed-off-by: Atish Patra <atishp(a)rivosinc.com> --- Changes in v3: - Dropped the redundant macros and rv32 specific csr details. - Changed to vcpu_get_reg from __vcpu_get_reg based on suggestion from Drew. - Added RB tags from Drew. - Link to v2: https://lore.kernel.org/r/20250429-kvm_selftest_improve-v2-0-51713f91e04a@r… Changes in v2: - Rebased on top of Linux 6.15-rc4 - Changed from ex_regs to pt_regs based on Drew's suggestion. - Dropped Anup's review on PATCH1 as it is significantly changed from last review. - Moved the instruction decoding macros to a common header file. - Improved the vector reg list test as per the feedback. - Link to v1: https://lore.kernel.org/r/20250324-kvm_selftest_improve-v1-0-583620219d4f@r… --- Atish Patra (3): KVM: riscv: selftests: Align the trap information wiht pt_regs KVM: riscv: selftests: Decode stval to identify exact exception type KVM: riscv: selftests: Add vector extension tests .../selftests/kvm/include/riscv/processor.h | 23 +++- tools/testing/selftests/kvm/lib/riscv/handlers.S | 139 +++++++++++---------- tools/testing/selftests/kvm/lib/riscv/processor.c | 2 +- tools/testing/selftests/kvm/riscv/arch_timer.c | 2 +- tools/testing/selftests/kvm/riscv/ebreak_test.c | 2 +- tools/testing/selftests/kvm/riscv/get-reg-list.c | 132 +++++++++++++++++++ tools/testing/selftests/kvm/riscv/sbi_pmu_test.c | 24 +++- 7 files changed, 247 insertions(+), 77 deletions(-) --- base-commit: f15d97df5afae16f40ecef942031235d1c6ba14f change-id: 20250324-kvm_selftest_improve-9bedb9f0a6d3 -- Regards, Atish patra

1 month, 1 week

[PATCH 0/2] Update kunit doc and tool with tips to build errors

by Shuah Khan

kunit kernel build could fail if there are ny build artifacts from a prior kernel build. These can be hard to debug if the build artifact happens to be generated header file. It took me a while to debug kunit build fail on ARCH=x86_64 in a tree which had a generated header file arch/x86/realmode/rm/pasyms.h make ARCH=um mrproper will not clean the tree. It is necessary to run make ARCH=x86_64 mrproper Example work-flow that could lead to this: make allmodconfig (x86_64) make ./tools/testing/kunit/kunit.py run Add this to the documentation and kunit.py build help message. Shuah Khan (2): doc: kunit: add information about cleaning source trees kunit: add tips to clean source tree to build help message Documentation/dev-tools/kunit/start.rst | 12 ++++++++++++ tools/testing/kunit/kunit.py | 2 +- 2 files changed, 13 insertions(+), 1 deletion(-) -- 2.47.2

1 month, 1 week

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Linux-kselftest-mirror May 2025