From: Jason Low <jason.low2@hp.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mel Gorman <mgorman@suse.de>,
Preeti U Murthy <preeti@linux.vnet.ibm.com>,
hideaki.kimura@hp.com, Aswin Chandramouleeswaran <aswin@hp.com>,
Scott J Norton <scott.norton@hp.com>,
jason.low2@hp.com
Subject: Re: [PATCH 1/3] sched, timer: Remove usages of ACCESS_ONCE in the scheduler
Date: Wed, 15 Apr 2015 19:29:01 -0700 [thread overview]
Message-ID: <1429151341.7039.162.camel@j-VirtualBox> (raw)
In-Reply-To: <20150414224059.061ec5bf@grimm.local.home>
On Tue, 2015-04-14 at 22:40 -0400, Steven Rostedt wrote:
> You are correct. Now I'm thinking that the WRITE_ONCE() is not needed,
> and just a:
>
> p->mm->numa_scan_seq = READ_ONCE(p->numa_scan_seq) + 1;
Just to confirm, is this a typo? Because there really is a numa_scan_seq
in the task_struct itself too :)
p->mm->numa_scan_seq is read in task_numa_placement() with
ACCESS_ONCE(), and so the benefit that I do see with it is that it makes
it consistent by doing the updates with ACCESS_ONCE too (for
documentation purposes).
If that's really the case:
WRITE_ONCE(p->mm->numa_scan_seq, p->mm->numa_scan_seq + 1)
should be enough for that.
next prev parent reply other threads:[~2015-04-16 2:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-14 23:09 [PATCH 0/3] sched, timer: Improve scalability of itimers Jason Low
2015-04-14 23:09 ` [PATCH 1/3] sched, timer: Remove usages of ACCESS_ONCE in the scheduler Jason Low
2015-04-14 23:59 ` Steven Rostedt
2015-04-15 2:12 ` Jason Low
2015-04-15 2:40 ` Steven Rostedt
2015-04-15 7:46 ` Ingo Molnar
2015-04-15 18:49 ` Jason Low
2015-04-15 19:16 ` Steven Rostedt
2015-04-16 2:46 ` Jason Low
2015-04-16 16:52 ` Peter Zijlstra
2015-04-16 18:02 ` Ingo Molnar
2015-04-16 18:15 ` Peter Zijlstra
2015-04-16 18:24 ` Ingo Molnar
2015-04-16 19:02 ` Peter Zijlstra
2015-04-16 19:41 ` Paul E. McKenney
2015-04-17 3:25 ` Jason Low
2015-04-17 8:19 ` Ingo Molnar
2015-04-16 21:00 ` Jason Low
2015-04-16 2:29 ` Jason Low [this message]
2015-04-16 2:37 ` Steven Rostedt
2015-04-14 23:09 ` [PATCH 2/3] sched, timer: Use atomics for thread_group_cputimer to improve scalability Jason Low
2015-04-15 7:33 ` Ingo Molnar
2015-04-15 7:35 ` Ingo Molnar
2015-04-15 17:14 ` Jason Low
2015-04-15 10:37 ` Preeti U Murthy
2015-04-15 19:09 ` Jason Low
2015-04-15 13:25 ` Frederic Weisbecker
2015-04-15 13:32 ` Peter Zijlstra
2015-04-15 20:04 ` Jason Low
2015-04-15 14:23 ` Davidlohr Bueso
2015-04-15 21:15 ` Jason Low
2015-04-14 23:09 ` [PATCH 3/3] sched, timer: Use cmpxchg to do updates in update_gt_cputime() Jason Low
2015-04-14 23:53 ` [PATCH 0/3] sched, timer: Improve scalability of itimers Linus Torvalds
2015-04-15 7:24 ` Ingo Molnar
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=1429151341.7039.162.camel@j-VirtualBox \
--to=jason.low2@hp.com \
--cc=akpm@linux-foundation.org \
--cc=aswin@hp.com \
--cc=fweisbec@gmail.com \
--cc=hideaki.kimura@hp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=preeti@linux.vnet.ibm.com \
--cc=rostedt@goodmis.org \
--cc=scott.norton@hp.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=umgwanakikbuti@gmail.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