Re: [PATCH RFC v3 13/13] uprobes: add speculative lockless VMA to inode resolution

[Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>]

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Sorry, nevermind, wrong forward :-/

On Thu, Aug 15, 2024, 4:17 PM Arnaldo Carvalho de Melo <
arnaldo.melo@gmail.com> wrote:

> Um exemplo de uma modificação numa área central derivada de uma
> necessidade específica: melhorar a performance de uprobes
>
> On Thu, Aug 15, 2024, 4:07 PM Mateusz Guzik <mjguzik@gmail.com> wrote:
>
>> On Thu, Aug 15, 2024 at 8:58 PM Jann Horn <jannh@google.com> wrote:
>> > Stupid question: Is this uprobe stuff actually such a hot codepath
>> > that it makes sense to optimize it to be faster than the page fault
>> > path?
>> >
>>
>> That's what I implicitly asked, hoping a down_read on vma would do it,
>> but Andrii claims multiple parallel lookups on the same vma are a
>> problem.
>>
>> Even so, I suspect something *simple* is doable here which avoids any
>> writes to vmas and does not need the mm-wide sequence counter. It may
>> be requirements are lax enough that merely observing some state is the
>> same before and after uprobe lookup will be sufficient, or maybe some
>> other hackery is viable without messing with fences in
>> vma_start_write.
>> --
>> Mateusz Guzik <mjguzik gmail.com>
>>
>>

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