linux-kernel - Re: [PATCH 00/10] perf/uprobe: Optimize uprobes

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Message-ID: <20240709090153.GF27299@noisy.programming.kicks-ass.net>
Date: Tue, 9 Jul 2024 11:01:53 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, mingo@...nel.org,
	andrii@...nel.org, linux-kernel@...r.kernel.org,
	rostedt@...dmis.org, oleg@...hat.com, jolsa@...nel.org,
	clm@...a.com, paulmck@...nel.org, bpf <bpf@...r.kernel.org>,
	willy@...radead.org
Subject: Re: [PATCH 00/10] perf/uprobe: Optimize uprobes

On Mon, Jul 08, 2024 at 05:25:14PM -0700, Andrii Nakryiko wrote:

> Quick profiling for the 8-threaded benchmark shows that we spend >20%
> in mmap_read_lock/mmap_read_unlock in find_active_uprobe. I think
> that's what would prevent uprobes from scaling linearly. If you have
> some good ideas on how to get rid of that, I think it would be
> extremely beneficial. 

That's find_vma() and friends. I started RCU-ifying that a *long* time
ago when I started the speculative page fault patches. I sorta lost
track of that effort, Willy where are we with that?

Specifically, how feasible would it be to get a simple RCU based
find_vma() version sorted these days?