From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: hch@infradead.org, mhocko@kernel.org, minchan@kernel.org,
ying.huang@intel.com, mgorman@techsingularity.net,
vdavydov.dev@gmail.com, hannes@cmpxchg.org,
akpm@linux-foundation.org, shakeelb@google.com,
gthelen@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm,vmscan: Kill global shrinker lock.
Date: Mon, 20 Nov 2017 10:28:38 -0800 [thread overview]
Message-ID: <20171120182838.GU3624@linux.vnet.ibm.com> (raw)
In-Reply-To: <201711201956.IIB86978.OFMVFFOJLtOSHQ@I-love.SAKURA.ne.jp>
On Mon, Nov 20, 2017 at 07:56:28PM +0900, Tetsuo Handa wrote:
> Christoph Hellwig wrote:
> > On Mon, Nov 20, 2017 at 10:42:37AM +0100, Michal Hocko wrote:
> > > The patch has been dropped because allnoconfig failed to compile back
> > > then http://lkml.kernel.org/r/CAP=VYLr0rPWi1aeuk4w1On9CYRNmnEWwJgGtaX=wEvGaBURtrg@mail.gmail.com
> > > I have problem to find the follow up discussion though. The main
> > > argument was that SRC is not generally available and so the core
> > > kernel should rely on it.
> >
> > Paul,
> >
> > isthere any good reason to not use SRCU in the core kernel and
> > instead try to reimplement it using atomic counters?
>
> CONFIG_SRCU was added in order to save system size. There are users who run Linux on very
> small systems ( https://www.elinux.org/images/5/52/Status-of-embedded-Linux-2017-09-JJ62.pdf ).
>
> Also, atomic counters are not mandatory for shrinker case; e.g.
> http://lkml.kernel.org/r/201711161956.EBF57883.QFFMOLOVSOHJFt@I-love.SAKURA.ne.jp .
CONFIG_SRCU was indeed added in order to shrink single-CPU systems.
But many architectures are now requiring SRCU for one reason or another,
in more and more situations.
So I recently implemented a UP-only Tiny SRCU, which is quite a bit
smaller than its scalable counterpart, Tree SRCU:
text data bss dec hex filename
983 64 0 1047 417 /tmp/c/kernel/rcu/srcutiny.o
text data bss dec hex filename
6844 193 0 7037 1b7d /tmp/b/kernel/rcu/srcutree.o
So perhaps it is time to unconditionally enable SRCU?
Thanx, Paul
prev parent reply other threads:[~2017-11-20 18:28 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-13 21:37 [PATCH 1/2] mm,vmscan: Kill global shrinker lock Tetsuo Handa
2017-11-13 21:37 ` [PATCH 2/2] mm,vmscan: Allow parallel registration/unregistration of shrinkers Tetsuo Handa
2017-11-13 22:05 ` [PATCH 1/2] mm,vmscan: Kill global shrinker lock Shakeel Butt
2017-11-15 0:56 ` Minchan Kim
2017-11-15 6:28 ` Shakeel Butt
2017-11-16 0:46 ` Minchan Kim
2017-11-16 1:41 ` Shakeel Butt
2017-11-16 4:50 ` Minchan Kim
2017-11-15 8:56 ` Michal Hocko
2017-11-15 9:18 ` Michal Hocko
2017-11-16 17:44 ` Johannes Weiner
2017-11-23 23:46 ` Minchan Kim
2017-11-15 9:02 ` Michal Hocko
2017-11-15 10:58 ` Tetsuo Handa
2017-11-15 11:51 ` Michal Hocko
2017-11-16 0:56 ` Minchan Kim
2017-11-15 13:28 ` Johannes Weiner
2017-11-16 10:56 ` Tetsuo Handa
2017-11-15 14:00 ` Johannes Weiner
2017-11-15 14:11 ` Michal Hocko
2018-01-25 2:04 ` Tetsuo Handa
2018-01-25 8:36 ` Michal Hocko
2018-01-25 10:56 ` Tetsuo Handa
2018-01-25 11:41 ` Michal Hocko
2018-01-25 22:19 ` Eric Wheeler
2018-01-26 3:12 ` Tetsuo Handa
2018-01-26 10:08 ` Michal Hocko
2017-11-17 17:35 ` Christoph Hellwig
2017-11-17 17:41 ` Shakeel Butt
2017-11-17 17:53 ` Shakeel Butt
2017-11-17 18:36 ` Christoph Hellwig
2017-11-20 9:25 ` Michal Hocko
2017-11-20 9:33 ` Christoph Hellwig
2017-11-20 9:42 ` Michal Hocko
2017-11-20 10:41 ` Christoph Hellwig
2017-11-20 10:56 ` Tetsuo Handa
2017-11-20 18:28 ` Paul E. McKenney [this message]
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