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| author | Yongliang Gao <leonylgao@tencent.com> | 2025-11-13 08:02:52 +0800 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-11-13 15:15:54 -0500 |
| commit | 97e047f44d347a4f4033c0b62f77a15a9deaf750 (patch) | |
| tree | 5e41ab10a0ea6043831fbb53e1df17df4bb37acb /kernel/trace/trace_functions_graph.c | |
| parent | e29aa918a928408c3e64b0d1025e4eb9f6fc549e (diff) | |
trace/pid_list: optimize pid_list->lock contention
When the system has many cores and task switching is frequent,
setting set_ftrace_pid can cause frequent pid_list->lock contention
and high system sys usage.
For example, in a 288-core VM environment, we observed 267 CPUs
experiencing contention on pid_list->lock, with stack traces showing:
#4 [ffffa6226fb4bc70] native_queued_spin_lock_slowpath at ffffffff99cd4b7e
#5 [ffffa6226fb4bc90] _raw_spin_lock_irqsave at ffffffff99cd3e36
#6 [ffffa6226fb4bca0] trace_pid_list_is_set at ffffffff99267554
#7 [ffffa6226fb4bcc0] trace_ignore_this_task at ffffffff9925c288
#8 [ffffa6226fb4bcd8] ftrace_filter_pid_sched_switch_probe at ffffffff99246efe
#9 [ffffa6226fb4bcf0] __schedule at ffffffff99ccd161
Replaces the existing spinlock with a seqlock to allow concurrent readers,
while maintaining write exclusivity.
Link: https://patch.msgid.link/20251113000252.1058144-1-leonylgao@gmail.com
Reviewed-by: Huang Cun <cunhuang@tencent.com>
Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_functions_graph.c')
0 files changed, 0 insertions, 0 deletions