From: Jose Fernandez <josef@netflix.com> mainline inclusion from mainline-v6.10-rc1 commit ce09cbdd988887662546a1175bcfdfc6c8fdd150 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ID7DOT Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- This patch improves the run-time calculation for program stats by capturing the duration as soon as possible after the program returns. Previously, the duration included u64_stats_t operations. While the instrumentation overhead is part of the total time spent when stats are enabled, distinguishing between the program's native execution time and the time spent due to instrumentation is crucial for accurate performance analysis. By making this change, the patch facilitates more precise optimization of BPF programs, enabling users to understand their performance in environments without stats enabled. I used a virtualized environment to measure the run-time over one minute for a basic raw_tracepoint/sys_enter program, which just increments a local counter. Although the virtualization introduced some performance degradation that could affect the results, I observed approximately a 16% decrease in average run-time reported by stats with this change (310 -> 260 nsec). Signed-off-by: Jose Fernandez <josef@netflix.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20240402034010.25060-1-josef@netflix.com Signed-off-by: Pu Lehui <pulehui@huawei.com> --- include/linux/filter.h | 6 ++++-- kernel/bpf/trampoline.c | 3 ++- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index a7c0caa8b7ad..7c16614df519 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -599,14 +599,16 @@ static __always_inline u32 __bpf_prog_run(const struct bpf_prog *prog, cant_migrate(); if (static_branch_unlikely(&bpf_stats_enabled_key)) { struct bpf_prog_stats *stats; - u64 start = sched_clock(); + u64 duration, start = sched_clock(); unsigned long flags; ret = dfunc(ctx, prog->insnsi, prog->bpf_func); + + duration = sched_clock() - start; stats = this_cpu_ptr(prog->stats); flags = u64_stats_update_begin_irqsave(&stats->syncp); u64_stats_inc(&stats->cnt); - u64_stats_add(&stats->nsecs, sched_clock() - start); + u64_stats_add(&stats->nsecs, duration); u64_stats_update_end_irqrestore(&stats->syncp, flags); } else { ret = dfunc(ctx, prog->insnsi, prog->bpf_func); diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index bcf8e4bad210..c20700f2a50f 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -906,12 +906,13 @@ static void notrace update_prog_stats(struct bpf_prog *prog, * Hence check that 'start' is valid. */ start > NO_START_TIME) { + u64 duration = sched_clock() - start; unsigned long flags; stats = this_cpu_ptr(prog->stats); flags = u64_stats_update_begin_irqsave(&stats->syncp); u64_stats_inc(&stats->cnt); - u64_stats_add(&stats->nsecs, sched_clock() - start); + u64_stats_add(&stats->nsecs, duration); u64_stats_update_end_irqrestore(&stats->syncp, flags); } } -- 2.34.1