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Message-Id: <20110818161751.9be5f1f9.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 18 Aug 2011 16:17:51 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Greg Thelen <gthelen@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
containers@...ts.osdl.org, linux-fsdevel@...r.kernel.org,
Balbir Singh <bsingharora@...il.com>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
Minchan Kim <minchan.kim@...il.com>,
Johannes Weiner <hannes@...xchg.org>,
Wu Fengguang <fengguang.wu@...el.com>,
Dave Chinner <david@...morbit.com>,
Vivek Goyal <vgoyal@...hat.com>,
Andrea Righi <andrea@...terlinux.com>,
Ciju Rajan K <ciju@...ux.vnet.ibm.com>,
David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH v9 11/13] writeback: make background writeback cgroup
aware
On Thu, 18 Aug 2011 00:10:56 -0700
Greg Thelen <gthelen@...gle.com> wrote:
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> writes:
>
> > On Wed, 17 Aug 2011 09:15:03 -0700
> > Greg Thelen <gthelen@...gle.com> wrote:
> >
> >> When the system is under background dirty memory threshold but some
> >> cgroups are over their background dirty memory thresholds, then only
> >> writeback inodes associated with the over-limit cgroups.
> >>
> >> In addition to checking if the system dirty memory usage is over the
> >> system background threshold, over_bground_thresh() now checks if any
> >> cgroups are over their respective background dirty memory thresholds.
> >>
> >> If over-limit cgroups are found, then the new
> >> wb_writeback_work.for_cgroup field is set to distinguish between system
> >> and memcg overages. The new wb_writeback_work.shared_inodes field is
> >> also set. Inodes written by multiple cgroup are marked owned by
> >> I_MEMCG_SHARED rather than a particular cgroup. Such shared inodes
> >> cannot easily be attributed to a cgroup, so per-cgroup writeback
> >> (futures version of wakeup_flusher_threads and balance_dirty_pages)
> >> performs suboptimally in the presence of shared inodes. Therefore,
> >> write shared inodes when performing cgroup background writeback.
> >>
> >> If performing cgroup writeback, move_expired_inodes() skips inodes that
> >> do not contribute dirty pages to the cgroup being written back.
> >>
> >> After writing some pages, wb_writeback() will call
> >> mem_cgroup_writeback_done() to update the set of over-bg-limits memcg.
> >>
> >> This change also makes wakeup_flusher_threads() memcg aware so that
> >> per-cgroup try_to_free_pages() is able to operate more efficiently
> >> without having to write pages of foreign containers. This change adds a
> >> mem_cgroup parameter to wakeup_flusher_threads() to allow callers,
> >> especially try_to_free_pages() and foreground writeback from
> >> balance_dirty_pages(), to specify a particular cgroup to write inodes
> >> from.
> >>
> >> Signed-off-by: Greg Thelen <gthelen@...gle.com>
> >> ---
> >> Changelog since v8:
> >>
> >> - Added optional memcg parameter to __bdi_start_writeback(),
> >> bdi_start_writeback(), wakeup_flusher_threads(), writeback_inodes_wb().
> >>
> >> - move_expired_inodes() now uses pass in struct wb_writeback_work instead of
> >> struct writeback_control.
> >>
> >> - Added comments to over_bground_thresh().
> >>
> >> fs/buffer.c | 2 +-
> >> fs/fs-writeback.c | 96 +++++++++++++++++++++++++++++++++-----------
> >> fs/sync.c | 2 +-
> >> include/linux/writeback.h | 6 ++-
> >> mm/backing-dev.c | 3 +-
> >> mm/page-writeback.c | 3 +-
> >> mm/vmscan.c | 3 +-
> >> 7 files changed, 84 insertions(+), 31 deletions(-)
> >>
> >> diff --git a/fs/buffer.c b/fs/buffer.c
> >> index dd0220b..da1fb23 100644
> >> --- a/fs/buffer.c
> >> +++ b/fs/buffer.c
> >> @@ -293,7 +293,7 @@ static void free_more_memory(void)
> >> struct zone *zone;
> >> int nid;
> >>
> >> - wakeup_flusher_threads(1024);
> >> + wakeup_flusher_threads(1024, NULL);
> >> yield();
> >>
> >> for_each_online_node(nid) {
> >> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> >> index e91fb82..ba55336 100644
> >> --- a/fs/fs-writeback.c
> >> +++ b/fs/fs-writeback.c
> >> @@ -38,10 +38,14 @@ struct wb_writeback_work {
> >> struct super_block *sb;
> >> unsigned long *older_than_this;
> >> enum writeback_sync_modes sync_mode;
> >> + unsigned short memcg_id; /* If non-zero, then writeback specified
> >> + * cgroup. */
> >> unsigned int tagged_writepages:1;
> >> unsigned int for_kupdate:1;
> >> unsigned int range_cyclic:1;
> >> unsigned int for_background:1;
> >> + unsigned int for_cgroup:1; /* cgroup writeback */
> >> + unsigned int shared_inodes:1; /* write inodes spanning cgroups */
> >>
> >> struct list_head list; /* pending work list */
> >> struct completion *done; /* set if the caller waits */
> >> @@ -114,9 +118,12 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
> >> spin_unlock_bh(&bdi->wb_lock);
> >> }
> >>
> >> +/*
> >> + * @memcg is optional. If set, then limit writeback to the specified cgroup.
> >> + */
> >> static void
> >> __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
> >> - bool range_cyclic)
> >> + bool range_cyclic, struct mem_cgroup *memcg)
> >> {
> >> struct wb_writeback_work *work;
> >>
> >> @@ -136,6 +143,8 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
> >> work->sync_mode = WB_SYNC_NONE;
> >> work->nr_pages = nr_pages;
> >> work->range_cyclic = range_cyclic;
> >> + work->memcg_id = memcg ? css_id(mem_cgroup_css(memcg)) : 0;
> >> + work->for_cgroup = memcg != NULL;
> >>
> >
> >
> > I couldn't find a patch for mem_cgroup_css(NULL). Is it in patch 1-10 ?
> > Other parts seems ok to me.
> >
> >
> > Thanks,
> > -Kame
>
> Mainline commit d324236b3333e87c8825b35f2104184734020d35 adds
> mem_cgroup_css() to memcontrol.c. The above code does not call
> mem_cgroup_css() with a NULL parameter due to the 'memcg ? ...' check.
> So I do not think any additional changes to mem_cgroup_css() are needed.
> Am I missing your point?
>
I thought you need
==
struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
{
+ if (!mem)
+ return NULL;
return &mem->css;
}
==
And
==
unsigned short css_id(struct cgroup_subsys_state *css)
{
struct css_id *cssid;
+ if (!css)
return 0;
}
==
Thanks,
-Kame
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