Changes in v2:
- Optimized the logic in descriptions. (Song Liu)
- Created a new header file to declare kfuncs for future extensions included by other files. (Christian Loehle)
- Fixed some logical issues in the code. (Christian Loehle)
Reference:
[1] https://lore.kernel.org/bpf/20250829101137.9507-1-yikai.lin@vivo.com/
Summary
----------
Hi, everyone,
This patch set introduces an extensible cpuidle governor framework
using BPF struct_ops, enabling dynamic implementation of idle-state selection policies
via BPF programs.
Motivation
----------
As is well-known, CPUs support multiple idle states (e.g., C0, C1, C2, ...),
where deeper states reduce power consumption, but results in longer wakeup latency,
potentially affecting performance.
Existing generic cpuidle governors operate effectively in common scenarios
but exhibit suboptimal behavior in specific Android phone's use cases.
Our testing reveals that during low-utilization scenarios
(e.g., screen-off background tasks like music playback with CPU utilization <10%),
the C0 state occupies ~50% of idle time, causing significant energy inefficiency.
Reducing C0 to ≤20% could yield ≥5% power savings on mobile phones.
To address this, we expect:
1.Dynamic governor switching to power-saved policies for low cpu utilization scenarios (e.g., screen-off mode)
2.Dynamic switching to alternate governors for high-performance scenarios (e.g., gaming)
OverView
----------
The BPF cpuidle ext governor registers at postcore_initcall()
but remains disabled by default due to its low priority "rating" with value "1".
Activation requires adjust higer "rating" than other governors within BPF.
Core Components:
1.**struct cpuidle_gov_ext_ops** – BPF-overridable operations:
- ops.enable()/ops.disable(): enable or disable callback
- ops.select(): cpu Idle-state selection logic
- ops.set_stop_tick(): Scheduler tick management after state selection
- ops.reflect(): feedback info about previous idle state.
- ops.init()/ops.deinit(): Initialization or cleanup.
2.**Critical kfuncs for kernel state access**:
- bpf_cpuidle_ext_gov_update_rating():
Activate ext governor by raising rating must be called from "ops.init()"
- bpf_cpuidle_ext_gov_latency_req(): get idle-state latency constraints
- bpf_tick_nohz_get_sleep_length(): get CPU sleep duration in tickless mode
Future work
----------
1. Scenario detection: Identifying low-utilization states (e.g., screen-off + background music)
2. Policy optimization: Optimizing state-selection algorithms for specific scenarios
Is it related to sched_ext?
---------------------------
The cpuidle framework is as follows.
----------------------------------------------------------
Scheduler Core
----------------------------------------------------------
|
v
----------------------------------------------------------
| FAIR Class | EXT Class | IDLE Class |
----------------------------------------------------------
| | | |
| | | v
| | | ------------------------
| | | enter_cpu_idle()
| | | ------------------------
| | | |
| | | v
| | | ------------------------------
| | | | CPUIDLE Governor |
| | | ------------------------------
| | | | | |
| | | v v v
| | |-----------------------------------
| | | default | | other | | BPF ext |
| | | Governor | | Governor | | Governor | <<===Here is the feature we add.
| | |-----------------------------------
| | | | | |
| | | v v v
| | |-------------------------------------
| | | select idle state
| | |-------------------------------------
Whereas cpuidle is invoked after switching to idle class when no tasks are present in the scheduling RQ.
They are not directly related, so implementing kfuncs or other extensions through sched_ext is not feasible.
Lin Yikai (2):
cpuidle: Implement BPF extensible cpuidle governor class
selftests/bpf: Add selftests for cpuidle_gov_ext
drivers/cpuidle/Kconfig | 12 +
drivers/cpuidle/governors/Makefile | 1 +
drivers/cpuidle/governors/ext.c | 537 ++++++++++++++++++
.../bpf/prog_tests/test_cpuidle_gov_ext.c | 28 +
.../selftests/bpf/progs/cpuidle_common.h | 13 +
.../selftests/bpf/progs/cpuidle_gov_ext.c | 200 +++++++
6 files changed, 791 insertions(+)
create mode 100644 drivers/cpuidle/governors/ext.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/test_cpuidle_gov_ext.c
create mode 100644 tools/testing/selftests/bpf/progs/cpuidle_common.h
create mode 100644 tools/testing/selftests/bpf/progs/cpuidle_gov_ext.c
--
2.43.0
From: Chia-Yu Chang <chia-yu.chang(a)nokia-bell-labs.com>
Hello,
Please find the v16 AccECN protocol patch series, which covers the core
functionality of Accurate ECN, AccECN negotiation, AccECN TCP options,
and AccECN failure handling. The Accurate ECN draft can be found in
https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-28, and it
will be RFC9768.
This patch series is part of the full AccECN patch series, which is available at
https://github.com/L4STeam/linux-net-next/commits/upstream_l4steam/
Best Regards,
Chia-Yu
---
v16 (6-Sep-2025)
- Use TCP_ECN_IN_ACCECN_OUT_ACCECN, TCP_ECN_IN_ECN_OUT_ECN, and TCP_ECN_IN_ACCECN_OUT_ECN in comments of tcp_ecn_send_syn() (Eric Dumazet <edumazet(a)google.com>)
- Add tcpi_accecn_fail_mode and tcpi_accecn_opt_seen to make tcp_info be multiple of 64 bits in patch #12
v15 (14-Aug-205)
- Update pahole results in commit messages
- Accurate ECN will become RFC9768
v14 (22-Jul-2025)
- Add missing const for struct tcp_sock of tcp_accecn_option_beacon_check() of #11 (Simon Horman <horms(a)kernel.org>)
v13 (18-Jul-2025)
- Implement tcp_accecn_extract_syn_ect() and tcp_accecn_reflector_flags() with static array lookup of patch #6 (Paolo Abeni <pabeni(a)redhat.com>)
- Fix typos in comments of #6 and remove patch #7 of v12 about simulatenous connect (Paolo Abeni <pabeni(a)redhat.com>)
- Move TCP_ACCECN_E1B_INIT_OFFSET, TCP_ACCECN_E0B_INIT_OFFSET, and TCP_ACCECN_CEB_INIT_OFFSET from patch #7 to #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Use static array lookup in tcp_accecn_optfield_to_ecnfield() of patch #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Return false when WARN_ON_ONCE() is true in tcp_accecn_process_option() of patch #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Make synack_ecn_bytes as static const array and use const u32 pointer in tcp_options_write() of #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Use ALIGN() and ALIGN_DOWN() in tcp_options_fit_accecn() to pad TCP AccECN option to dword of #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Return TCP_ACCECN_OPT_FAIL_SEEN if WARN_ON_ONCE() is true in tcp_accecn_option_init() of #12 (Paolo Abeni <pabeni(a)redhat.com>)
v12 (04-Jul-2025)
- Fix compilation issues with some intermediate patches in v11
- Add more comments for AccECN helpers of tcp_ecn.h
v11 (03-Jul-2025)
- Fix compilation issues with some intermediate patches in v10
v10 (02-Jul-2025)
- Add new patch of separated header file include/net/tcp_ecn.h to include ECN and AccECN functions (Eric Dumazet <edumazet(a)google.com>)
- Add comments on the AccECN helper functions in tcp_ecn.h (Eric Dumazet <edumazet(a)google.com>)
- Add documentation of tcp_ecn, tcp_ecn_option, tcp_ecn_beacon in ip-sysctl.rst to the corresponding patch (Eric Dumazet <edumazet(a)google.com>)
- Split wait third ACK functionality into a separated patch from AccECN negotiation patch (Eric Dumazet <edumazet(a)google.com>)
- Add READ_ONCE() over every reads of sysctl for all patches in the series (Eric Dumazet <edumazet(a)google.com>)
- Merge heuristics of AccECN option ceb/cep and ACE field multi-wrap into a single patch
- Add a table of SACK block reduction and required AccECN field in patch #15 commit message (Eric Dumazet <edumazet(a)google.com>)
v9 (21-Jun-2025)
- Use tcp_data_ecn_check() to set TCP_ECN_SEE flag only for RFC3168 ECN (Paolo Abeni <pabeni(a)redhat.com>)
- Add comments about setting TCP_ECN_SEEN flag for RFC3168 and Accruate ECN (Paolo Abeni <pabeni(a)redhat.com>)
- Restruct the code in the for loop of tcp_accecn_process_option() (Paolo Abeni <pabeni(a)redhat.com>)
- Remove ecn_bytes and add use_synack_ecn_bytes flag to identify whether syn_ack_bytes or received_ecn_bytes is used (Paolo Abeni <pabeni(a)redhat.com>)
- Replace leftover_bytes and leftover_size with leftover_highbyte and leftover_lowbyte and add comments in tcp_options_write() (Paolo Abeni <pabeni(a)redhat.com>)
- Add comments and commit message about the 1st retx SYN still attempt AccECN negotiation (Paolo Abeni <pabeni(a)redhat.com>)
v8 (10-Jun-2025)
- Add new helper function tcp_ecn_received_counters_payload() in #6 (Paolo Abeni <pabeni(a)redhat.com>)
- Set opts->num_sack_blocks=0 to avoid potential undefined value in #8 (Paolo Abeni <pabeni(a)redhat.com>)
- Reset leftover_size to 2 once leftover_bytes is used in #9 (Paolo Abeni <pabeni(a)redhat.com>)
- Add new helper function tcp_accecn_opt_demand_min() in #10 (Paolo Abeni <pabeni(a)redhat.com>)
- Add new helper function tcp_accecn_saw_opt_fail_recv() in #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Update tcp_options_fit_accecn() to avoid using recursion in #14 (Paolo Abeni <pabeni(a)redhat.com>)
v7 (14-May-2025)
- Modify group sizes of tcp_sock_write_txrx and tcp_sock_write_rx in #3 based on pahole results (Paolo Abeni <pabeni(a)redhat.com>)
- Fix the issue in #4 and #5 where the RFC3168 ECN behavior in tcp_ecn_send() is changed (Paolo Abeni <pabeni(a)redhat.com>)
- Modify group size of tcp_sock_write_txrx in #4 and #6 based on pahole results (Paolo Abeni <pabeni(a)redhat.com>)
- Update commit message for #9 to explain the increase in tcp_sock_write_rx group size
- Modify group size of tcp_sock_write_tx in #10 based on pahole results
v6 (09-May-2025)
- Add #3 to utilize exisintg holes of tcp_sock_write_txrx group for later patches (#4, #9, #10) with new u8 members (Paolo Abeni <pabeni(a)redhat.com>)
- Add pahole outcomes before and after commit in #4, #5, #6, #9, #10, #15 (Paolo Abeni <pabeni(a)redhat.com>)
- Define new helper function tcp_send_ack_reflect_ect() for sending ACK with reflected ECT in #5 (Paolo Abeni <pabeni(a)redhat.com>)
- Add comments for function tcp_ecn_rcv_synack() in #5 (Paolo Abeni <pabeni(a)redhat.com>)
- Add enum/define to be used by sysctl_tcp_ecn in #5, sysctl_tcp_ecn_option in #9, and sysctl_tcp_ecn_option_beacon in #10 (Paolo Abeni <pabeni(a)redhat.com>)
- Move accecn_fail_mode and saw_accecn_opt in #5 and #11 to use exisintg holes of tcp_sock (Paolo Abeni <pabeni(a)redhat.com>)
- Change data type of new members of tcp_request_sock and move them to the end of struct in #5 and #11 (Paolo Abeni <pabeni(a)redhat.com>)
- Move new members of tcp_info to the end of struct in #6 (Paolo Abeni <pabeni(a)redhat.com>)
- Merge previous #7 into #9 (Paolo Abeni <pabeni(a)redhat.com>)
- Mask ecnfield with INET_ECN_MASK to remove WARN_ONCE in #9 (Paolo Abeni <pabeni(a)redhat.com>)
- Reduce the indentation levels for reabability in #9 and #10 (Paolo Abeni <pabeni(a)redhat.com>)
- Move delivered_ecn_bytes to the RX group in #9, accecn_opt_tstamp to the TX group in #10, pkts_acked_ewma to the RX group in #15 (Paolo Abeni <pabeni(a)redhat.com>)
- Add changes in Documentation/networking/net_cachelines/tcp_sock.rst for new tcp_sock members in #3, #5, #6, #9, #10, #15
v5 (22-Apr-2025)
- Further fix for 32-bit ARM alignment in tcp.c (Simon Horman <horms(a)kernel.org>)
v4 (18-Apr-2025)
- Fix 32-bit ARM assertion for alignment requirement (Simon Horman <horms(a)kernel.org>)
v3 (14-Apr-2025)
- Fix patch apply issue in v2 (Jakub Kicinski <kuba(a)kernel.org>)
v2 (18-Mar-2025)
- Add one missing patch from the previous AccECN protocol preparation patch series to this patch series.
---
Chia-Yu Chang (5):
tcp: reorganize tcp_sock_write_txrx group for variables later
tcp: ecn functions in separated include file
tcp: accecn: AccECN option send control
tcp: accecn: AccECN option failure handling
tcp: accecn: try to fit AccECN option with SACK
Ilpo Järvinen (9):
tcp: reorganize SYN ECN code
tcp: fast path functions later
tcp: AccECN core
tcp: accecn: AccECN negotiation
tcp: accecn: add AccECN rx byte counters
tcp: accecn: AccECN needs to know delivered bytes
tcp: sack option handling improvements
tcp: accecn: AccECN option
tcp: accecn: AccECN option ceb/cep and ACE field multi-wrap heuristics
Documentation/networking/ip-sysctl.rst | 55 +-
.../networking/net_cachelines/tcp_sock.rst | 12 +
include/linux/tcp.h | 32 +-
include/net/netns/ipv4.h | 2 +
include/net/tcp.h | 87 ++-
include/net/tcp_ecn.h | 642 ++++++++++++++++++
include/uapi/linux/tcp.h | 9 +
net/ipv4/syncookies.c | 4 +
net/ipv4/sysctl_net_ipv4.c | 19 +
net/ipv4/tcp.c | 30 +-
net/ipv4/tcp_input.c | 353 ++++++++--
net/ipv4/tcp_ipv4.c | 8 +-
net/ipv4/tcp_minisocks.c | 40 +-
net/ipv4/tcp_output.c | 294 ++++++--
net/ipv6/syncookies.c | 2 +
net/ipv6/tcp_ipv6.c | 1 +
16 files changed, 1406 insertions(+), 184 deletions(-)
create mode 100644 include/net/tcp_ecn.h
--
2.34.1
devmem test fails on NIPA. Most likely we get skb(s) with readable
frags (why?) but the failure manifests as an OOM. The OOM happens
because ncdevmem spams the following message:
recvmsg ret=-1
recvmsg: Bad address
As of today, ncdevmem can't deal with various reasons of EFAULT:
- falling back to regular recvmsg for non-devmem skbs
- increasing ctrl_data size (can't happen with ncdevmem's large buffer)
Exit (cleanly) with error when recvmsg returns EFAULT. This should at
least cause the test to cleanup its state.
Signed-off-by: Stanislav Fomichev <sdf(a)fomichev.me>
---
tools/testing/selftests/drivers/net/hw/ncdevmem.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
index 8dc9511d046f..c0a22938bed2 100644
--- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c
+++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c
@@ -945,6 +945,10 @@ static int do_server(struct memory_buffer *mem)
continue;
if (ret < 0) {
perror("recvmsg");
+ if (errno == EFAULT) {
+ pr_err("received EFAULT, won't recover");
+ goto err_close_client;
+ }
continue;
}
if (ret == 0) {
--
2.51.0
Create a netconsole test that puts a lot of pressure on the netconsole
list manipulation. Do it by creating dynamic targets and deleting
targets while messages are being sent. Also put interface down while the
In order to do it, refactor create_dynamic_target(), so it can be used to
create random targets in the torture test.
Signed-off-by: Breno Leitao <leitao(a)debian.org>
---
Changes in v2:
- Reuse the netconsole creation from lib_netcons.sh. Thus, refactoring
the create_dynamic_target() (Jakub)
- Move the "wait" to after all the messages has been sent.
- Link to v1: https://lore.kernel.org/r/20250902-netconsole_torture-v1-1-03c6066598e9@deb…
---
Breno Leitao (2):
selftest: netcons: refactor target creation
selftest: netcons: create a torture test
tools/testing/selftests/drivers/net/Makefile | 1 +
.../selftests/drivers/net/lib/sh/lib_netcons.sh | 30 +++--
.../selftests/drivers/net/netcons_torture.sh | 127 +++++++++++++++++++++
3 files changed, 147 insertions(+), 11 deletions(-)
---
base-commit: 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
change-id: 20250902-netconsole_torture-8fc23f0aca99
Best regards,
--
Breno Leitao <leitao(a)debian.org>