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Message-ID: <20241022073141.3291245-3-liaochang1@huawei.com>
Date: Tue, 22 Oct 2024 07:31:41 +0000
From: Liao Chang <liaochang1@...wei.com>
To: <andrii.nakryiko@...il.com>, <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>
CC: <linux-kernel@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>,
<linux-perf-users@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: [PATCH v4 2/2] uprobes: Remove the spinlock within handle_singlestep()
This patch introduces a flag to track TIF_SIGPENDING is suppress
temporarily during the uprobe single-step. Upon uprobe singlestep is
handled and the flag is confirmed, it could resume the TIF_SIGPENDING
directly without acquiring the siglock in most case, then reducing
contention and improving overall performance.
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 for get_xol_insn_slot() [2].
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.
[1] https://lore.kernel.org/all/20240731214256.3588718-1-andrii@kernel.org
[2] https://lore.kernel.org/all/20240727094405.1362496-1-liaochang1@huawei.com
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Acked-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
include/linux/uprobes.h | 1 +
kernel/events/uprobes.c | 8 +++++---
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 2b294bf1881f..1c5ece4ed55b 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -76,6 +76,7 @@ struct uprobe_task {
struct uprobe *active_uprobe;
unsigned long xol_vaddr;
+ bool signal_denied;
struct arch_uprobe *auprobe;
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 196366c013f2..315efbee4353 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1986,6 +1986,7 @@ bool uprobe_deny_signal(void)
WARN_ON_ONCE(utask->state != UTASK_SSTEP);
if (task_sigpending(t)) {
+ utask->signal_denied = true;
clear_tsk_thread_flag(t, TIF_SIGPENDING);
if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
@@ -2302,9 +2303,10 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
utask->state = UTASK_RUNNING;
xol_free_insn_slot(utask);
- spin_lock_irq(¤t->sighand->siglock);
- recalc_sigpending(); /* see uprobe_deny_signal() */
- spin_unlock_irq(¤t->sighand->siglock);
+ if (utask->signal_denied) {
+ set_thread_flag(TIF_SIGPENDING);
+ utask->signal_denied = false;
+ }
if (unlikely(err)) {
uprobe_warn(current, "execute the probed insn, sending SIGILL.");
--
2.34.1
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