Re: [PATCH v2] io_uring/rsrc: fix RLIMIT_MEMLOCK bypass by removing cross-buffer accounting

[Pavel Begunkov]

On 1/24/26 15:55, Jens Axboe wrote:
> On 1/24/26 8:14 AM, Jens Axboe wrote:
> > > > ________________________________________________________
> > > > Executed in    2.81 secs    fish           external
> > > >      usr time    0.71 secs  497.00 micros    0.71 secs
> > > >      sys time   19.57 secs  183.00 micros   19.57 secs
> > > >
> > > > which isn't insane. Obviously also needs conditional rescheduling in the
> > > > page loops, as those can take a loooong time for large amounts of
> > > > memory.
> > >
> > > 2.8 sec sounds like a lot as well, makes me wonder which part of
> > > that is mm, but it mm should scale fine-ish. Surely there will be
> > > contention on page refcounts but at least the table walk is
> > > lockless in the best case scenario and otherwise seems to be read
> > > protected by an rw lock.
> >
> > Well a lot of that is also just faulting in the memory on clear, test
> > case should probably be modified to do its own timing. And iterating
> > page arrays is a huge part of it too. There's no real contention in that
> > 2.8 seconds.
>
> I checked and the faulting part is 2.0s of that runtime. On a re-run:

Makes sense, I was forgetting it's full time.

--
Pavel Begunkov