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charset="UTF-8" Content-Transfer-Encoding: quoted-printable Um exemplo de uma modifica=C3=A7=C3=A3o numa =C3=A1rea central derivada de = uma necessidade espec=C3=ADfica: melhorar a performance de uprobes On Thu, Aug 15, 2024, 4:07=E2=80=AFPM Mateusz Guzik wro= te: > On Thu, Aug 15, 2024 at 8:58=E2=80=AFPM Jann Horn wrot= e: > > 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 > > --0000000000003be472061fbdb1b5 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Um exemplo de uma modifica=C3=A7=C3=A3o numa =C3=A1rea centr= al derivada de uma necessidade espec=C3=ADfica: melhorar a performance de u= probes


On Thu= , Aug 15, 2024, 4:07=E2=80=AFPM Mateusz Guzik <mjguzik@gmail.com> wrote:
On Thu, Aug 15, 2024 at 8:58=E2=80=AFPM 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,<= br> 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>

--0000000000003be472061fbdb1b5--