[lkml]   [2020]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 2/2] mm: proc: smaps_rollup: do not stall write attempts on mmap_lock
On Fri, 2020-08-14 at 01:35 -0700, Michel Lespinasse wrote:
> On Wed, Aug 12, 2020 at 7:13 PM Chinwen Chang
> <> wrote:
> > smaps_rollup will try to grab mmap_lock and go through the whole vma
> > list until it finishes the iterating. When encountering large processes,
> > the mmap_lock will be held for a longer time, which may block other
> > write requests like mmap and munmap from progressing smoothly.
> >
> > There are upcoming mmap_lock optimizations like range-based locks, but
> > the lock applied to smaps_rollup would be the coarse type, which doesn't
> > avoid the occurrence of unpleasant contention.
> >
> > To solve aforementioned issue, we add a check which detects whether
> > anyone wants to grab mmap_lock for write attempts.
> I think your retry mechanism still doesn't handle all cases. When you
> get back the mmap lock, the address where you stopped last time could
> now be in the middle of a vma. I think the consistent thing to do in
> that case would be to retry scanning from the address you stopped at,
> even if it's not on a vma boundary anymore. You may have to change
> smap_gather_stats to support that, though.

Hi Michel,

I think I got your point. Let me try to prepare new patch series for
further reviews.

Thank you for your suggestion :)

 \ /
  Last update: 2020-08-14 11:09    [W:0.210 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site