From: Yang Shi <shy828301@gmail.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>, Kirill Tkhai <ktkhai@virtuozzo.com>,
Shakeel Butt <shakeelb@google.com>,
Dave Chinner <david@fromorbit.com>,
Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux MM <linux-mm@kvack.org>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered
Date: Fri, 4 Dec 2020 13:24:04 -0800 [thread overview]
Message-ID: <CAHbLzkqf5=C6dMJjHzqNMZUSdO_eONd9ciOsUE-CdHGqkvBTJQ@mail.gmail.com> (raw)
In-Reply-To: <20201204185247.GA182921@cmpxchg.org>
On Fri, Dec 4, 2020 at 10:54 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Thu, Dec 03, 2020 at 02:25:20PM -0800, Yang Shi wrote:
> > On Thu, Dec 3, 2020 at 12:09 PM Roman Gushchin <guro@fb.com> wrote:
> > >
> > > On Wed, Dec 02, 2020 at 08:59:40PM -0800, Yang Shi wrote:
> > > > On Wed, Dec 2, 2020 at 7:01 PM Roman Gushchin <guro@fb.com> wrote:
> > > > >
> > > > > On Wed, Dec 02, 2020 at 10:27:20AM -0800, Yang Shi wrote:
> > > > > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred.
> > > > > > This approach is fine with nr_deferred atthe shrinker level, but the following
> > > > > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their
> > > > > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers
> > > > > > from unregistering correctly.
> > > > > >
> > > > > > Introduce a new "state" field to indicate if shrinker is registered or not.
> > > > > > We could use the highest bit of flags, but it may be a little bit complicated to
> > > > > > extract that bit and the flags is accessed frequently by vmscan (every time shrinker
> > > > > > is called). So add a new field in "struct shrinker", we may waster a little bit
> > > > > > memory, but it should be very few since there should be not too many registered
> > > > > > shrinkers on a normal system.
> > > > > >
> > > > > > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > > > > > ---
> > > > > > include/linux/shrinker.h | 4 ++++
> > > > > > mm/vmscan.c | 13 +++++++++----
> > > > > > 2 files changed, 13 insertions(+), 4 deletions(-)
> > > > > >
> > > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> > > > > > index 0f80123650e2..0bb5be88e41d 100644
> > > > > > --- a/include/linux/shrinker.h
> > > > > > +++ b/include/linux/shrinker.h
> > > > > > @@ -35,6 +35,9 @@ struct shrink_control {
> > > > > >
> > > > > > #define SHRINK_STOP (~0UL)
> > > > > > #define SHRINK_EMPTY (~0UL - 1)
> > > > > > +
> > > > > > +#define SHRINKER_REGISTERED 0x1
> > > > > > +
> > > > > > /*
> > > > > > * A callback you can register to apply pressure to ageable caches.
> > > > > > *
> > > > > > @@ -66,6 +69,7 @@ struct shrinker {
> > > > > > long batch; /* reclaim batch size, 0 = default */
> > > > > > int seeks; /* seeks to recreate an obj */
> > > > > > unsigned flags;
> > > > > > + unsigned state;
> > > > >
> > > > > Hm, can't it be another flag? It seems like we have a plenty of free bits.
> > > >
> > > > I thought about this too. But I was not convinced by myself that
> > > > messing flags with state is a good practice. We may add more flags in
> > > > the future, so we may end up having something like:
> > > >
> > > > flag
> > > > flag
> > > > flag
> > > > state
> > > > flag
> > > > flag
> > > > ...
> > > >
> > > > Maybe we could use the highest bit for state?
> > >
> > > Or just
> > > state
> > > flag
> > > flag
> > > flag
> > > flag
> > > flag
> > > ...
> > >
> > > ?
> >
> > It is fine too. We should not add more states in foreseeable future.
>
> It's always possible to shuffle things around for cleanup later on,
> too. We don't have to provide binary compatibility for existing flags,
> and changing a couple of adjacent bits isn't a big deal to keep things
> neat. Or am I missing something?
No. It is definitely not a big deal.
next prev parent reply other threads:[~2020-12-04 21:24 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 18:27 [RFC PATCH 0/9] Make shrinker's nr_deferred memcg aware Yang Shi
2020-12-02 18:27 ` [PATCH 1/9] mm: vmscan: simplify nr_deferred update code Yang Shi
2020-12-03 2:56 ` Roman Gushchin
2020-12-02 18:27 ` [PATCH 2/9] mm: vmscan: use nid from shrink_control for tracepoint Yang Shi
2020-12-03 3:13 ` Xiaqing (A)
2020-12-11 19:20 ` Yang Shi
2020-12-02 18:27 ` [PATCH 3/9] mm: memcontrol: rename memcg_shrinker_map_mutex to memcg_shrinker_mutex Yang Shi
2020-12-02 18:27 ` [PATCH 4/9] mm: vmscan: use a new flag to indicate shrinker is registered Yang Shi
2020-12-03 3:01 ` Roman Gushchin
2020-12-03 4:59 ` Yang Shi
2020-12-03 20:08 ` Roman Gushchin
2020-12-03 22:25 ` Yang Shi
2020-12-04 18:52 ` Johannes Weiner
2020-12-04 21:24 ` Yang Shi [this message]
2020-12-02 18:27 ` [PATCH 5/9] mm: memcontrol: add per memcg shrinker nr_deferred Yang Shi
2020-12-03 3:06 ` Roman Gushchin
2020-12-03 4:54 ` Yang Shi
2020-12-03 18:03 ` Yang Shi
2020-12-03 20:07 ` Roman Gushchin
2020-12-03 22:49 ` Yang Shi
2020-12-03 23:30 ` Roman Gushchin
2020-12-04 0:22 ` Yang Shi
2020-12-10 15:33 ` Johannes Weiner
2020-12-10 19:12 ` Yang Shi
2020-12-11 17:52 ` Yang Shi
2020-12-10 21:59 ` Yang Shi
2020-12-02 18:27 ` [PATCH 6/9] mm: vmscan: use per memcg nr_deferred of shrinker Yang Shi
2020-12-03 3:08 ` Roman Gushchin
2020-12-03 5:01 ` Yang Shi
2020-12-03 11:40 ` Kirill Tkhai
2020-12-08 17:13 ` Yang Shi
2020-12-09 15:41 ` Kirill Tkhai
2020-12-09 17:32 ` Yang Shi
2020-12-10 15:13 ` Johannes Weiner
2020-12-10 15:17 ` Kirill Tkhai
2020-12-15 16:44 ` Johannes Weiner
2020-12-02 18:27 ` [PATCH 7/9] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers Yang Shi
2020-12-02 18:27 ` [PATCH 8/9] mm: memcontrol: reparent nr_deferred when memcg offline Yang Shi
2020-12-02 18:27 ` [PATCH 9/9] mm: vmscan: shrink deferred objects proportional to priority Yang Shi
2020-12-03 2:52 ` [RFC PATCH 0/9] Make shrinker's nr_deferred memcg aware Roman Gushchin
2020-12-03 17:52 ` Yang Shi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAHbLzkqf5=C6dMJjHzqNMZUSdO_eONd9ciOsUE-CdHGqkvBTJQ@mail.gmail.com' \
--to=shy828301@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=david@fromorbit.com \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=ktkhai@virtuozzo.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=shakeelb@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).