lkml.org 
[lkml]   [2018]   [Aug]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker
On Wed 01-08-18 19:12:25, Wei Wang wrote:
> On 07/30/2018 05:00 PM, Michal Hocko wrote:
> > On Fri 27-07-18 17:24:55, Wei Wang wrote:
> > > The OOM notifier is getting deprecated to use for the reasons mentioned
> > > here by Michal Hocko: https://lkml.org/lkml/2018/7/12/314
> > >
> > > This patch replaces the virtio-balloon oom notifier with a shrinker
> > > to release balloon pages on memory pressure.
> > It would be great to document the replacement. This is not a small
> > change...
>
> OK. I plan to document the following to the commit log:
>
> The OOM notifier is getting deprecated to use for the reasons:
> - As a callout from the oom context, it is too subtle and easy to
> generate bugs and corner cases which are hard to track;
> - It is called too late (after the reclaiming has been performed).
> Drivers with large amuont of reclaimable memory is expected to be
> released them at an early age of memory pressure;
> - The notifier callback isn't aware of the oom contrains;
> Link: https://lkml.org/lkml/2018/7/12/314
>
> This patch replaces the virtio-balloon oom notifier with a shrinker
> to release balloon pages on memory pressure. Users can set the amount of
> memory pages to release each time a shrinker_scan is called via the
> module parameter balloon_pages_to_shrink, and the default amount is 256
> pages. Historically, the feature VIRTIO_BALLOON_F_DEFLATE_ON_OOM has
> been used to release balloon pages on OOM. We continue to use this
> feature bit for the shrinker, so the shrinker is only registered when
> this feature bit has been negotiated with host.

Do you have any numbers for how does this work in practice? Let's say
you have a medium page cache workload which triggers kswapd to do a
light reclaim? Hardcoded shrinking sounds quite dubious to me but I have
no idea how people expect this to work. Shouldn't this be more
adaptive? How precious are those pages anyway?
--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2018-08-01 13:35    [W:0.072 / U:0.700 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site