linux-kernel - Re: [PATCH -next v1 0/3] kernel/events/uprobes: uprobe_write

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Message-ID: <CAEf4BzbyFy0eQHLac3zR8GiGDOUqYoTGAWDbFaeou903OGOTpg@mail.gmail.com>
Date: Wed, 5 Mar 2025 11:43:52 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: David Hildenbrand <david@...hat.com>, Andrii Nakryiko <andrii@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, linux-trace-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Matthew Wilcox <willy@...radead.org>, Russell King <linux@...linux.org.uk>, 
	Masami Hiramatsu <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>, Ian Rogers <irogers@...gle.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, "Liang, Kan" <kan.liang@...ux.intel.com>, 
	Tong Tiangen <tongtiangen@...wei.com>
Subject: Re: [PATCH -next v1 0/3] kernel/events/uprobes: uprobe_write_opcode() rewrite

On Wed, Mar 5, 2025 at 7:22 AM Oleg Nesterov <oleg@...hat.com> wrote:
>
> On 03/04, David Hildenbrand wrote:
> >
> > Currently, uprobe_write_opcode() implements COW-breaking manually, which is
> > really far from ideal.
>
> To say at least ;)
>
> David, thanks for doing this. I'll try to read 3/3 tomorrow, but I don't
> think I can really help. Let me repeat, this code was written many years
> ago, I forgot everything, and today my understanding of mm/ is very poor.
> But I'll try anyway.
>
> > Are there any uprobe tests / benchmarks that are worth running?
>
> All I know about uprobe tests is that bpf people run a lot of tests which
> use uprobes.
>
> Andrii, Jiri, what you advise?
>

We do have a bunch of tests within BPF selftests:

cd tools/testing/selftest/bpf && make -j$(nproc) && sudo ./test_progs -t uprobe

I also built an uprobe-stress tool to validate uprobe optimizations I
was doing, this one is the most stand-alone thing to use for testing,
please consider checking that. You can find it at [0], and see also
[1] and [2] where  I was helping Peter to build it from sources, so
that might be useful for you as well, if you run into problems with
building. Running something like `sudo ./uprobe-stress -a10 -t5 -m5
-f3` would hammer on this quite a bit.

I'm just about to leave on a short vacation, so won't have time to go
over patches, but I plan to look at them when I'm back next week.

  [0] https://github.com/libbpf/libbpf-bootstrap/tree/uprobe-stress
  [1] https://lore.kernel.org/linux-trace-kernel/CAEf4BzZ+ygwfk8FKn5AS_Ny=igvGcFzdDLE2FjcvwjCKazEWMA@mail.gmail.com/
  [2] https://lore.kernel.org/linux-trace-kernel/CAEf4BzZqKCR-EQz6LTi-YvFY4RnYb_NnQXtwgZCv6aUo7gjkHg@mail.gmail.com

> Oleg.
>