Message-ID: <CAEf4BzY-0Eu27jyT_s2kRO1UuUPOkE9_SRrBOqu2gJfmxsv+3A@mail.gmail.com>
Date: Tue, 5 Nov 2024 18:07:20 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Liao Chang <liaochang1@...wei.com>
Cc: mhiramat@...nel.org, oleg@...hat.com, peterz@...radead.org, 
	mingo@...hat.com, acme@...nel.org, namhyung@...nel.org, mark.rutland@....com, 
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com, 
	adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v4 0/2] uprobes: Improve scalability by reducing the
 contention on siglock

On Tue, Oct 22, 2024 at 12:42 AM Liao Chang <liaochang1@...wei.com> wrote:
>
> The profiling result of BPF selftest on ARM64 platform reveals the
> significant contention on the current->sighand->siglock is the
> scalability bottleneck. The reason is also very straightforward that all
> producer threads of benchmark have to contend the spinlock mentioned to
> resume the TIF_SIGPENDING bit in thread_info that might be removed in
> uprobe_deny_signal().
>
> The contention on current->sighand->siglock is unnecessary, this series
> remove them thoroughly. I've use the script developed by Andrii in [1]
> to run benchmark. The CPU used was Kunpeng916 (Hi1616), 4 NUMA nodes,
> 64 cores@...GHz running the kernel on next tree + the optimization in
> [2] for get_xol_insn_slot().
>
> before-opt
> ----------
> uprobe-nop      ( 1 cpus):    0.907 ± 0.003M/s  (  0.907M/s/cpu)
> uprobe-nop      ( 2 cpus):    1.676 ± 0.008M/s  (  0.838M/s/cpu)
> uprobe-nop      ( 4 cpus):    3.210 ± 0.003M/s  (  0.802M/s/cpu)
> uprobe-nop      ( 8 cpus):    4.457 ± 0.003M/s  (  0.557M/s/cpu)
> uprobe-nop      (16 cpus):    3.724 ± 0.011M/s  (  0.233M/s/cpu)
> uprobe-nop      (32 cpus):    2.761 ± 0.003M/s  (  0.086M/s/cpu)
> uprobe-nop      (64 cpus):    1.293 ± 0.015M/s  (  0.020M/s/cpu)
>
> uprobe-push     ( 1 cpus):    0.883 ± 0.001M/s  (  0.883M/s/cpu)
> uprobe-push     ( 2 cpus):    1.642 ± 0.005M/s  (  0.821M/s/cpu)
> uprobe-push     ( 4 cpus):    3.086 ± 0.002M/s  (  0.771M/s/cpu)
> uprobe-push     ( 8 cpus):    3.390 ± 0.003M/s  (  0.424M/s/cpu)
> uprobe-push     (16 cpus):    2.652 ± 0.005M/s  (  0.166M/s/cpu)
> uprobe-push     (32 cpus):    2.713 ± 0.005M/s  (  0.085M/s/cpu)
> uprobe-push     (64 cpus):    1.313 ± 0.009M/s  (  0.021M/s/cpu)
>
> uprobe-ret      ( 1 cpus):    1.774 ± 0.000M/s  (  1.774M/s/cpu)
> uprobe-ret      ( 2 cpus):    3.350 ± 0.001M/s  (  1.675M/s/cpu)
> uprobe-ret      ( 4 cpus):    6.604 ± 0.000M/s  (  1.651M/s/cpu)
> uprobe-ret      ( 8 cpus):    6.706 ± 0.005M/s  (  0.838M/s/cpu)
> uprobe-ret      (16 cpus):    5.231 ± 0.001M/s  (  0.327M/s/cpu)
> uprobe-ret      (32 cpus):    5.743 ± 0.003M/s  (  0.179M/s/cpu)
> uprobe-ret      (64 cpus):    4.726 ± 0.016M/s  (  0.074M/s/cpu)
>
> after-opt
> ---------
> uprobe-nop      ( 1 cpus):    0.985 ± 0.002M/s  (  0.985M/s/cpu)
> uprobe-nop      ( 2 cpus):    1.773 ± 0.005M/s  (  0.887M/s/cpu)
> uprobe-nop      ( 4 cpus):    3.304 ± 0.001M/s  (  0.826M/s/cpu)
> uprobe-nop      ( 8 cpus):    5.328 ± 0.002M/s  (  0.666M/s/cpu)
> uprobe-nop      (16 cpus):    6.475 ± 0.002M/s  (  0.405M/s/cpu)
> uprobe-nop      (32 cpus):    4.831 ± 0.082M/s  (  0.151M/s/cpu)
> uprobe-nop      (64 cpus):    2.564 ± 0.053M/s  (  0.040M/s/cpu)
>
> uprobe-push     ( 1 cpus):    0.964 ± 0.001M/s  (  0.964M/s/cpu)
> uprobe-push     ( 2 cpus):    1.766 ± 0.002M/s  (  0.883M/s/cpu)
> uprobe-push     ( 4 cpus):    3.290 ± 0.009M/s  (  0.823M/s/cpu)
> uprobe-push     ( 8 cpus):    4.670 ± 0.002M/s  (  0.584M/s/cpu)
> uprobe-push     (16 cpus):    5.197 ± 0.004M/s  (  0.325M/s/cpu)
> uprobe-push     (32 cpus):    5.068 ± 0.161M/s  (  0.158M/s/cpu)
> uprobe-push     (64 cpus):    2.605 ± 0.026M/s  (  0.041M/s/cpu)
>
> uprobe-ret      ( 1 cpus):    1.833 ± 0.001M/s  (  1.833M/s/cpu)
> uprobe-ret      ( 2 cpus):    3.384 ± 0.003M/s  (  1.692M/s/cpu)
> uprobe-ret      ( 4 cpus):    6.677 ± 0.004M/s  (  1.669M/s/cpu)
> uprobe-ret      ( 8 cpus):    6.854 ± 0.005M/s  (  0.857M/s/cpu)
> uprobe-ret      (16 cpus):    6.508 ± 0.006M/s  (  0.407M/s/cpu)
> uprobe-ret      (32 cpus):    5.793 ± 0.009M/s  (  0.181M/s/cpu)
> uprobe-ret      (64 cpus):    4.743 ± 0.016M/s  (  0.074M/s/cpu)
>
> Above benchmark results demonstrates a obivious improvement in the
> scalability of trig-uprobe-nop and trig-uprobe-push, the peak throughput
> of which are from 4.5M/s to 6.4M/s and 3.3M/s to 5.1M/s individually.
>
> v4->v3:
> 1. Rebase v3 [3] to the lateset tip/perf/core.
> 2. Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 3. Acked-by: Oleg Nesterov <oleg@...hat.com>
>
> v3->v2:
> Renaming the flag in [2/2], s/deny_signal/signal_denied/g.
>
> v2->v1:
> Oleg pointed out the _DENY_SIGNAL will be replaced by _ACK upon the
> completion of singlestep which leads to handle_singlestep() has no
> chance to restore the removed TIF_SIGPENDING [3] and some case in
> question. So this revision proposes to use a flag in uprobe_task to
> track the denied TIF_SIGPENDING instead of new UPROBE_SSTEP state.
>
> [1] https://lore.kernel.org/all/20240731214256.3588718-1-andrii@kernel.org
> [2] https://lore.kernel.org/all/20240727094405.1362496-1-liaochang1@huawei.com
> [3] https://lore.kernel.org/all/20240815014629.2685155-1-liaochang1@huawei.com/
>
> Liao Chang (2):
>   uprobes: Remove redundant spinlock in uprobe_deny_signal()
>   uprobes: Remove the spinlock within handle_singlestep()
>
>  include/linux/uprobes.h |  1 +
>  kernel/events/uprobes.c | 10 +++++-----
>  2 files changed, 6 insertions(+), 5 deletions(-)
>
> --
> 2.34.1
>

This patch set has been ready for a long while, can we please apply it
to perf/core as well? Thank you!

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