linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	jack-AlSwsSmVLrQ@public.gmane.org,
	hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	mhocko-AlSwsSmVLrQ@public.gmane.org,
	clm-b10kYP2dOMg@public.gmane.org,
	fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org,
	gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org
Subject: Re: [PATCH 01/19] memcg: make mem_cgroup_read_{stat|event}() iterate possible cpus instead of online
Date: Fri, 22 May 2015 19:12:49 -0400	[thread overview]
Message-ID: <20150522231249.GA6485@cmpxchg.org> (raw)
In-Reply-To: <1432333416-6221-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

On Fri, May 22, 2015 at 06:23:18PM -0400, Tejun Heo wrote:
> cpu_possible_mask represents the CPUs which are actually possible
> during that boot instance.  For systems which don't support CPU
> hotplug, this will match cpu_online_mask exactly in most cases.  Even
> for systems which support CPU hotplug, the number of possible CPU
> slots is highly unlikely to diverge greatly from the number of online
> CPUs.  The only cases where the difference between possible and online
> caused problems were when the boot code failed to initialize the
> possible mask and left it fully set at NR_CPUS - 1.
> 
> As such, most per-cpu constructs allocate for all possible CPUs and
> often iterate over the possibles, which also has the benefit of
> avoiding the blocking CPU hotplug synchronization.
> 
> memcg open codes per-cpu stat counting for mem_cgroup_read_stat() and
> mem_cgroup_read_events(), which iterates over online CPUs and handles
> CPU hotplug operations explicitly.  This complexity doesn't actually
> buy anything.  Switch to iterating over the possibles and drop the
> explicit CPU hotplug handling.
> 
> Eventually, we want to convert memcg to use percpu_counter instead of
> its own custom implementation which also benefits from quick access
> w/o summing for cases where larger error margin is acceptable.
> 
> This will allow mem_cgroup_read_stat() to be called from non-sleepable
> contexts which will be used by cgroup writeback.
> 
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> Cc: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>

Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>

  parent reply	other threads:[~2015-05-22 23:12 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-22 22:23 [PATCHSET 2/3 v3 block/for-4.2/core] writeback: cgroup writeback backpressure propagation Tejun Heo
2015-05-22 22:23 ` [PATCH 01/19] memcg: make mem_cgroup_read_{stat|event}() iterate possible cpus instead of online Tejun Heo
     [not found]   ` <1432333416-6221-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2015-05-22 23:12     ` Johannes Weiner [this message]
2015-06-17 14:41   ` Michal Hocko
2015-05-22 22:23 ` [PATCH 02/19] writeback: clean up wb_dirty_limit() Tejun Heo
2015-05-22 22:23 ` [PATCH 03/19] writeback: reorganize [__]wb_update_bandwidth() Tejun Heo
2015-05-22 22:23 ` [PATCH 04/19] writeback: implement wb_domain Tejun Heo
2015-05-22 22:23 ` [PATCH 05/19] writeback: move global_dirty_limit into wb_domain Tejun Heo
2015-05-22 22:23 ` [PATCH 06/19] writeback: consolidate dirty throttle parameters into dirty_throttle_control Tejun Heo
2015-05-22 22:23 ` [PATCH 07/19] writeback: add dirty_throttle_control->wb_bg_thresh Tejun Heo
2015-05-22 22:23 ` [PATCH 08/19] writeback: make __wb_calc_thresh() take dirty_throttle_control Tejun Heo
2015-05-22 22:23 ` [PATCH 09/19] writeback: add dirty_throttle_control->pos_ratio Tejun Heo
2015-05-22 22:23 ` [PATCH 10/19] writeback: add dirty_throttle_control->wb_completions Tejun Heo
2015-05-22 22:23 ` [PATCH 11/19] writeback: add dirty_throttle_control->dom Tejun Heo
2015-05-22 22:23 ` [PATCH 12/19] writeback: make __wb_writeout_inc() and hard_dirty_limit() take wb_domaas a parameter Tejun Heo
2015-05-22 22:23 ` [PATCH 13/19] writeback: separate out domain_dirty_limits() Tejun Heo
2015-05-22 22:23 ` [PATCH 14/19] writeback: move over_bground_thresh() to mm/page-writeback.c Tejun Heo
2015-05-22 22:23 ` [PATCH 15/19] writeback: update wb_over_bg_thresh() to use wb_domain aware operations Tejun Heo
2015-05-22 22:23 ` [PATCH 16/19] writeback: implement memcg wb_domain Tejun Heo
2015-05-22 22:23 ` [PATCH 17/19] writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes Tejun Heo
2015-05-22 22:23 ` [PATCH 18/19] writeback: implement memcg writeback domain based throttling Tejun Heo
2015-05-22 22:23 ` [PATCH 19/19] mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use Tejun Heo
  -- strict thread matches above, loose matches on Subject: below --
2015-04-06 20:04 [PATCHSET 2/3 v2 block/for-4.1/core] writeback: cgroup writeback backpressure propagation Tejun Heo
2015-04-06 20:04 ` [PATCH 01/19] memcg: make mem_cgroup_read_{stat|event}() iterate possible cpus instead of online Tejun Heo

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=20150522231249.GA6485@cmpxchg.org \
    --to=hannes-druugvl0lcnafugrpc6u6w@public.gmane.org \
    --cc=axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org \
    --cc=cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=clm-b10kYP2dOMg@public.gmane.org \
    --cc=david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org \
    --cc=fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org \
    --cc=gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org \
    --cc=hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org \
    --cc=jack-AlSwsSmVLrQ@public.gmane.org \
    --cc=khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org \
    --cc=linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
    --cc=linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org \
    --cc=lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org \
    --cc=mhocko-AlSwsSmVLrQ@public.gmane.org \
    --cc=tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org \
    --cc=vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org \
    --subject='Re: [PATCH 01/19] memcg: make mem_cgroup_read_{stat|event}() iterate possible cpus instead of online' \
    /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

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).