From: Shakeel Butt <shakeelb@google.com>
To: josh@joshtriplett.org
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>,
Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
gregkh@linuxfoundation.org, rafael@kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
Hugh Dickins <hughd@google.com>,
shuah@kernel.org, robh@kernel.org, ulf.hansson@linaro.org,
aspriel@gmail.com, vivek.gautam@codeaurora.org,
robin.murphy@arm.com, joe@perches.com,
heikki.krogerus@linux.intel.com,
Stephen Rothwell <sfr@canb.auug.org.au>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Chris Wilson <chris@chris-wilson.co.uk>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Matthew Wilcox <willy@infradead.org>,
Huang Ying <ying.huang@intel.com>,
jbacik@fb.com, Ingo Molnar <mingo@kernel.org>,
mhiramat@kernel.org, LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled
Date: Wed, 8 Aug 2018 16:02:29 -0700 [thread overview]
Message-ID: <CALvZod7C_jcNc=J0wg_wnCa2fkCjHhjoV1G8oKAmivRbvgQWxg@mail.gmail.com> (raw)
In-Reply-To: <20180808180152.GA2480@localhost>
On Wed, Aug 8, 2018 at 11:02 AM Josh Triplett <josh@joshtriplett.org> wrote:
>
> On Wed, Aug 08, 2018 at 07:30:13PM +0300, Kirill Tkhai wrote:
> > On 08.08.2018 19:23, Kirill Tkhai wrote:
> > > On 08.08.2018 19:13, Josh Triplett wrote:
> > >> On Wed, Aug 08, 2018 at 01:17:44PM +0300, Kirill Tkhai wrote:
> > >>> On 08.08.2018 10:20, Michal Hocko wrote:
> > >>>> On Tue 07-08-18 18:37:36, Kirill Tkhai wrote:
> > >>>>> This patch kills all CONFIG_SRCU defines and
> > >>>>> the code under !CONFIG_SRCU.
> > >>>>
> > >>>> The last time somebody tried to do this there was a pushback due to
> > >>>> kernel tinyfication. So this should really give some numbers about the
> > >>>> code size increase. Also why can't we make this depend on MMU. Is
> > >>>> anybody else than the reclaim asking for unconditional SRCU usage?
> > >>>
> > >>> I don't know one. The size numbers (sparc64) are:
> > >>>
> > >>> $ size image.srcu.disabled
> > >>> text data bss dec hex filename
> > >>> 5117546 8030506 1968104 15116156 e6a77c image.srcu.disabled
> > >>> $ size image.srcu.enabled
> > >>> text data bss dec hex filename
> > >>> 5126175 8064346 1968104 15158625 e74d61 image.srcu.enabled
> > >>> The difference is: 15158625-15116156 = 42469 ~41Kb
> > >>
> > >> 41k is a *substantial* size increase. However, can you compare
> > >> tinyconfig with and without this patch? That may have a smaller change.
> > >
> > > $ size image.srcu.disabled
> > > text data bss dec hex filename
> > > 1105900 195456 63232 1364588 14d26c image.srcu.disabled
> > >
> > > $ size image.srcu.enabled
> > > text data bss dec hex filename
> > > 1106960 195528 63232 1365720 14d6d8 image.srcu.enabled
> > >
> > > 1365720-1364588 = 1132 ~ 1Kb
> >
> > 1Kb is not huge size. It looks as not a big price for writing generic code
> > for only case (now some places have CONFIG_SRCU and !CONFIG_SRCU variants,
> > e.g. drivers/base/core.c). What do you think?
>
> That's a little more reasonable than 41k, likely because of
> CONFIG_TINY_SRCU. That's still not ideal, though. And as far as I can
> tell, the *only* two pieces of core code that use SRCU are
> drivers/base/core.c and kernel/notifier.c, and the latter is exclusively
> code to use notifiers with SRCU, not notifiers wanting to use SRCU
> themselves. So, as far as I can tell, this would really just save a
> couple of small #ifdef sections in drivers/base/core.c, and I think
> those #ifdef sections could be simplified even further. That doesn't
> seem worth it at all.
Hi Josh, the motivation behind enabling SRCU is not to simplify the
code in drivers/base/core.c but rather not to introduce similar ifdefs
in mm/vmscan.c for shrinker traversals.
Shakeel
next prev parent reply other threads:[~2018-08-08 23:02 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 15:37 [PATCH RFC 00/10] Introduce lockless shrink_slab() Kirill Tkhai
2018-08-07 15:37 ` [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled Kirill Tkhai
2018-08-08 0:55 ` Steven Rostedt
2018-08-08 1:05 ` Stephen Rothwell
2018-08-08 9:46 ` Kirill Tkhai
2018-08-08 1:08 ` Stephen Rothwell
2018-08-08 9:59 ` Kirill Tkhai
2018-08-08 11:04 ` Stephen Rothwell
2018-08-08 7:20 ` Michal Hocko
2018-08-08 10:17 ` Kirill Tkhai
2018-08-08 10:27 ` Michal Hocko
2018-08-08 21:31 ` Dave Chinner
2018-08-09 0:07 ` Matthew Wilcox
2018-08-09 7:45 ` Greg KH
2018-08-09 10:22 ` Kirill Tkhai
2018-08-08 16:13 ` Josh Triplett
2018-08-08 16:23 ` Kirill Tkhai
2018-08-08 16:30 ` Kirill Tkhai
2018-08-08 18:01 ` Josh Triplett
2018-08-08 23:02 ` Shakeel Butt [this message]
2018-08-08 23:09 ` Josh Triplett
2018-08-07 15:37 ` [PATCH RFC 02/10] mm: Make shrink_slab() lockless Kirill Tkhai
2018-08-08 11:51 ` Kirill Tkhai
2018-08-08 13:20 ` [PATCH RFC v2 " Kirill Tkhai
2018-08-09 7:14 ` Michal Hocko
2018-08-09 9:21 ` Kirill Tkhai
2018-08-09 10:37 ` Tetsuo Handa
2018-08-09 10:58 ` Kirill Tkhai
2018-08-09 11:23 ` Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 03/10] mm: Convert shrinker_rwsem to mutex Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 04/10] mm: Split unregister_shrinker() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 05/10] fs: Move list_lru_destroy() to destroy_super_work() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 06/10] fs: Shrink only (SB_ACTIVE|SB_BORN) superblocks in super_cache_scan() Kirill Tkhai
2018-08-07 15:38 ` [PATCH RFC 07/10] fs: Introduce struct super_operations::destroy_super() callback Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 08/10] xfs: Introduce xfs_fs_destroy_super() Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 09/10] shmem: Implement shmem_destroy_super() Kirill Tkhai
2018-08-07 15:39 ` [PATCH RFC 10/10] fs: Use unregister_shrinker_delayed_{initiate, finalize} for super_block shrinker Kirill Tkhai
2018-08-08 1:12 ` [PATCH RFC 00/10] Introduce lockless shrink_slab() Stephen Rothwell
2018-08-08 5:39 ` Shakeel Butt
2018-08-08 10:18 ` Kirill Tkhai
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