From: Shakeel Butt <shakeelb@google.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Philippe Ombredanne <pombredanne@nexb.com>,
stummala@codeaurora.org, gregkh@linuxfoundation.org,
Stephen Rothwell <sfr@canb.auug.org.au>,
Roman Gushchin <guro@fb.com>,
mka@chromium.org,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Chris Wilson <chris@chris-wilson.co.uk>,
longman@redhat.com, Minchan Kim <minchan@kernel.org>,
Huang Ying <ying.huang@intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
jbacik@fb.com, Guenter Roeck <linux@roeck-us.net>,
LKML <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
lirongqing@baidu.com, Andrey Ryabinin <aryabinin@virtuozzo.com>,
Andrew Morton <akpm@linux-foundation.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker
Date: Tue, 3 Jul 2018 10:00:32 -0700 [thread overview]
Message-ID: <CALvZod6eomn1Mt5r28tMthq4b+3MWuWJKgishf_N4UjortzvHw@mail.gmail.com> (raw)
In-Reply-To: <a9fe3e9e-a1b7-ee19-35e6-af32b5f25a37@virtuozzo.com>
On Tue, Jul 3, 2018 at 9:17 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
> Hi, Shakeel,
>
> On 03.07.2018 18:46, Shakeel Butt wrote:
> > On Tue, Jul 3, 2018 at 8:27 AM Matthew Wilcox <willy@infradead.org> wrote:
> >>
> >> On Tue, Jul 03, 2018 at 06:09:05PM +0300, Kirill Tkhai wrote:
> >>> +++ b/mm/vmscan.c
> >>> @@ -169,6 +169,49 @@ unsigned long vm_total_pages;
> >>> static LIST_HEAD(shrinker_list);
> >>> static DECLARE_RWSEM(shrinker_rwsem);
> >>>
> >>> +#ifdef CONFIG_MEMCG_KMEM
> >>> +static DEFINE_IDR(shrinker_idr);
> >>> +static int shrinker_nr_max;
> >>
> >> So ... we've now got a list_head (shrinker_list) which contains all of
> >> the shrinkers, plus a shrinker_idr which contains the memcg-aware shrinkers?
> >>
> >> Why not replace the shrinker_list with the shrinker_idr? It's only used
> >> twice in vmscan.c:
> >>
> >> void register_shrinker_prepared(struct shrinker *shrinker)
> >> {
> >> down_write(&shrinker_rwsem);
> >> list_add_tail(&shrinker->list, &shrinker_list);
> >> up_write(&shrinker_rwsem);
> >> }
> >>
> >> list_for_each_entry(shrinker, &shrinker_list, list) {
> >> ...
> >>
> >> The first is simply idr_alloc() and the second is
> >>
> >> idr_for_each_entry(&shrinker_idr, shrinker, id) {
> >>
> >> I understand there's a difference between allocating the shrinker's ID and
> >> adding it to the list. You can do this by calling idr_alloc with NULL
> >> as the pointer, and then using idr_replace() when you want to add the
> >> shrinker to the list. idr_for_each_entry() skips over NULL entries.
> >>
> >> This will actually reduce the size of each shrinker and be more
> >> cache-efficient when calling the shrinkers. I think we can also get
> >> rid of the shrinker_rwsem eventually, but let's leave it for now.
> >
> > Can you explain how you envision shrinker_rwsem can be removed? I am
> > very much interested in doing that.
>
> Have you tried to do some games with SRCU? It looks like we just need to
> teach count_objects() and scan_objects() to work with semi-destructed
> shrinkers. Though, this looks this will make impossible to introduce
> shrinkers, which do synchronize_srcu() in scan_objects() for example.
> Not sure, someone will actually use this, and this is possible to consider
> as limitation.
>
Hi Kirill, I tried SRCU and the discussion is at
https://lore.kernel.org/lkml/20171117173521.GA21692@infradead.org/T/#u
Paul E. McKenney suggested to enable SRCU unconditionally. So, to use
SRCU for shrinkers, we first have to push unconditional SRCU.
Tetsuo had another lockless solution which was a bit involved but does
not depend on SRCU.
thanks,
Shakeel
next prev parent reply other threads:[~2018-07-03 17:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-03 15:08 [PATCH v8 00/17] Improve shrink_slab() scalability (old complexity was O(n^2), new is O(n)) Kirill Tkhai
2018-07-03 15:08 ` [PATCH v8 01/17] list_lru: Combine code under the same define Kirill Tkhai
2018-07-03 15:08 ` [PATCH v8 02/17] mm: Introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 03/17] mm: Assign id to every memcg-aware shrinker Kirill Tkhai
2018-07-03 15:27 ` Matthew Wilcox
2018-07-03 15:46 ` Shakeel Butt
2018-07-03 16:17 ` Kirill Tkhai
2018-07-03 17:00 ` Shakeel Butt [this message]
2018-07-03 17:32 ` Kirill Tkhai
2018-07-12 11:13 ` Kirill Tkhai
2018-07-12 11:19 ` Kirill Tkhai
2018-07-03 17:47 ` Matthew Wilcox
2018-07-03 20:39 ` Al Viro
2018-07-03 15:46 ` Kirill Tkhai
2018-07-03 17:58 ` Matthew Wilcox
2018-07-03 19:12 ` Kirill Tkhai
2018-07-03 19:19 ` Shakeel Butt
2018-07-03 19:25 ` Matthew Wilcox
2018-07-03 19:54 ` Shakeel Butt
2018-07-03 15:09 ` [PATCH v8 04/17] memcg: Move up for_each_mem_cgroup{, _tree} defines Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 05/17] mm: Assign memcg-aware shrinkers bitmap to memcg Kirill Tkhai
2018-07-03 20:50 ` Andrew Morton
2018-07-04 15:51 ` Kirill Tkhai
2018-07-05 22:10 ` Andrew Morton
2018-07-06 17:50 ` Vladimir Davydov
2018-07-05 22:50 ` Matthew Wilcox
2018-07-06 17:30 ` Vladimir Davydov
2018-07-03 15:09 ` [PATCH v8 06/17] mm: Refactoring in workingset_init() Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 07/17] fs: Refactoring in alloc_super() Kirill Tkhai
2018-07-03 15:09 ` [PATCH v8 08/17] fs: Propagate shrinker::id to list_lru Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 09/17] list_lru: Add memcg argument to list_lru_from_kmem() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 10/17] list_lru: Pass dst_memcg argument to memcg_drain_list_lru_node() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 11/17] list_lru: Pass lru " Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 12/17] mm: Export mem_cgroup_is_root() Kirill Tkhai
2018-07-03 15:10 ` [PATCH v8 13/17] mm: Set bit in memcg shrinker bitmap on first list_lru item apearance Kirill Tkhai
2018-07-03 20:54 ` Andrew Morton
2018-07-03 15:11 ` [PATCH v8 14/17] mm: Iterate only over charged shrinkers during memcg shrink_slab() Kirill Tkhai
2018-07-03 20:58 ` Andrew Morton
2018-07-04 14:56 ` Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 15/17] mm: Generalize shrink_slab() calls in shrink_node() Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 16/17] mm: Add SHRINK_EMPTY shrinker methods return value Kirill Tkhai
2018-07-03 15:11 ` [PATCH v8 17/17] mm: Clear shrinker bit if there are no objects related to memcg Kirill Tkhai
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=CALvZod6eomn1Mt5r28tMthq4b+3MWuWJKgishf_N4UjortzvHw@mail.gmail.com \
--to=shakeelb@google.com \
--cc=akpm@linux-foundation.org \
--cc=aryabinin@virtuozzo.com \
--cc=chris@chris-wilson.co.uk \
--cc=gregkh@linuxfoundation.org \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=jbacik@fb.com \
--cc=ktkhai@virtuozzo.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@roeck-us.net \
--cc=lirongqing@baidu.com \
--cc=longman@redhat.com \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=minchan@kernel.org \
--cc=mka@chromium.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=pombredanne@nexb.com \
--cc=sfr@canb.auug.org.au \
--cc=stummala@codeaurora.org \
--cc=tglx@linutronix.de \
--cc=vdavydov.dev@gmail.com \
--cc=viro@zeniv.linux.org.uk \
--cc=willy@infradead.org \
--cc=ying.huang@intel.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).