From: "Huang\, Ying" <ying.huang@intel.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Hugh Dickins" <hughd@google.com>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
"Minchan Kim" <minchan@kernel.org>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
"Mel Gorman" <mgorman@techsingularity.net>,
"J�r�me Glisse" <jglisse@redhat.com>,
"Michal Hocko" <mhocko@suse.com>,
"David Rientjes" <rientjes@google.com>,
"Rik van Riel" <riel@redhat.com>, "Jan Kara" <jack@suse.cz>,
"Dave Jiang" <dave.jiang@intel.com>,
"Daniel Jordan" <daniel.m.jordan@oracle.com>,
"Andrea Parri" <andrea.parri@amarulasolutions.com>
Subject: Re: [PATCH -mm -V7] mm, swap: fix race between swapoff and some swap operations
Date: Fri, 15 Feb 2019 15:50:21 +0800 [thread overview]
Message-ID: <87mumxa3sy.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20190214214741.GB10698@redhat.com> (Andrea Arcangeli's message of "Thu, 14 Feb 2019 16:47:41 -0500")
Andrea Arcangeli <aarcange@redhat.com> writes:
> On Thu, Feb 14, 2019 at 04:07:37PM +0800, Huang, Ying wrote:
>> Before, we choose to use stop_machine() to reduce the overhead of hot
>> path (page fault handler) as much as possible. But now, I found
>> rcu_read_lock_sched() is just a wrapper of preempt_disable(). So maybe
>> we can switch to RCU version now.
>
> rcu_read_lock looks more efficient than rcu_read_lock_sched. So for
> this purpose in the fast path rcu_read_lock()/unlock() should be the
> preferred methods, no need to force preempt_disable() (except for
> debug purposes if sleep debug is enabled). Server builds are done with
> voluntary preempt (no preempt shouldn't even exist as config option)
> and there rcu_read_lock might be just a noop.
If
CONFIG_PREEMPT_VOLUNTARY=y
CONFIG_PREEMPT=n
CONFIG_PREEMPT_COUNT=n
which is common for servers,
rcu_read_lock() will be a noop, rcu_read_lock_sched() and
preempt_disable() will be barrier(). So rcu_read_lock() is a little
better.
> Against a fast path rcu_read_lock/unlock before the consolidation
> synchronize_rcu would have been enough, now after the consolidation
> even more certain that it's enough because it's equivalent to _mult.
Yes. Will change to rcu_read_lock/unlock based method.
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2019-02-15 7:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 8:38 [PATCH -mm -V7] mm, swap: fix race between swapoff and some swap operations Huang, Ying
2019-02-11 19:06 ` Daniel Jordan
2019-02-12 3:21 ` Andrea Parri
[not found] ` <874l99ld05.fsf@yhuang-dev.intel.com>
2019-02-12 17:58 ` Tim Chen
2019-02-13 3:23 ` Huang, Ying
2019-02-12 20:06 ` Daniel Jordan
2019-02-12 6:40 ` Huang, Ying
2019-02-12 10:13 ` Andrea Parri
2019-02-14 2:38 ` Andrea Arcangeli
[not found] ` <87k1i2oks6.fsf@yhuang-dev.intel.com>
2019-02-14 21:47 ` Andrea Arcangeli
2019-02-15 7:50 ` Huang, Ying [this message]
2019-02-14 14:33 ` Michal Hocko
2019-02-14 20:30 ` Andrew Morton
2019-02-14 21:22 ` Andrea Arcangeli
[not found] ` <871s49bkaz.fsf@yhuang-dev.intel.com>
2019-02-15 13:11 ` Michal Hocko
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=87mumxa3sy.fsf@yhuang-dev.intel.com \
--to=ying.huang@intel.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=andrea.parri@amarulasolutions.com \
--cc=daniel.m.jordan@oracle.com \
--cc=dave.jiang@intel.com \
--cc=hannes@cmpxchg.org \
--cc=hughd@google.com \
--cc=jack@suse.cz \
--cc=jglisse@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@suse.com \
--cc=minchan@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
--cc=tim.c.chen@linux.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).