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

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Message-ID: <62f93f79-a8d4-44a5-b276-3ac5af4ab25c@redhat.com>
Date: Wed, 5 Mar 2025 20:47:51 +0100
From: David Hildenbrand <david@...hat.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>,
 Oleg Nesterov <oleg@...hat.com>
Cc: 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 05.03.25 20:43, Andrii Nakryiko wrote:
> 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 stumbled over them, but was so far not successful in building them in 
my test VM (did not try too hard, though). Will try harder now that I 
know that it actually tests uprobe properly :)

> 
> 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.

Thanks, I'll play with that as well.

> 
> 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.
>>
> 


-- 
Cheers,

David / dhildenb