linux-kernel - Re: [PATCH] uprobes: reduce contention on uprobes

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Message-ID: <syviklbpdblcwr3l2seuwyzfrg2hy2shx5f6ho6yf4s4ce63tc@nbo4by247y6z>
Date: Mon, 25 Mar 2024 19:12:29 +0000
From: Jonthan Haslam <jonathan.haslam@...il.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, andrii@...nel.org, 
	bpf@...r.kernel.org, rostedt@...dmis.org, mhiramat@...nel.org, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes: reduce contention on uprobes_tree access

Hi Ingo,

> > This change has been tested against production workloads that exhibit
> > significant contention on the spinlock and an almost order of magnitude
> > reduction for mean uprobe execution time is observed (28 -> 3.5 microsecs).
> 
> Have you considered/measured per-CPU RW semaphores?

No I hadn't but thanks hugely for suggesting it! In initial measurements
it seems to be between 20-100% faster than the RW spinlocks! Apologies for
all the exclamation marks but I'm very excited. I'll do some more testing
tomorrow but so far it's looking very good.

Thanks again for the input.

Jon.