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

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Message-ID: <Zo1lrpO3suceheVj@casper.infradead.org>
Date: Tue, 9 Jul 2024 17:30:38 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	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, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH 00/10] perf/uprobe: Optimize uprobes

On Tue, Jul 09, 2024 at 05:10:45PM +0100, Matthew Wilcox wrote:
> > So I fundamentally do not believe in per-VMA locking. Specifically for
> > this case that would be trading one hot line for another. I tried
> > telling people that, but it doesn't seem to stick :/
> 
> SRCU also had its own performance problems, so we've got problems one
> way or the other.  The per-VMA lock probably doesn't work quite the way
> you think it does, but it absoutely can be a hot cacheline.
> 
> I did propose a store-free variant at LSFMM 2022 and again at 2023,
> but was voted down.  https://lwn.net/Articles/932298/

Actually, the 2022 version has a bit more of the flavour of the
argument: https://lwn.net/Articles/893906/