From: Hugh Dickins <hughd@google.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Ying Han <yinghan@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/10] mm/memcg: take care over pc->mem_cgroup
Date: Tue, 21 Feb 2012 15:03:03 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.00.1202211437140.2012@eggly.anvils> (raw)
In-Reply-To: <20120221181321.637556cd.kamezawa.hiroyu@jp.fujitsu.com>
On Tue, 21 Feb 2012, KAMEZAWA Hiroyuki wrote:
> On Mon, 20 Feb 2012 15:34:28 -0800 (PST)
> Hugh Dickins <hughd@google.com> wrote:
> return NULL;
> >
> > + lruvec = page_lock_lruvec(page);
> > lock_page_cgroup(pc);
> >
>
> Do we need to take lrulock+irq disable per page in this very very hot path ?
I'm sure we don't want to: I hope you were pleased to find it goes away
(from most cases) a couple of patches later.
I had lruvec lock nested inside page_cgroup lock in the rollup I sent in
December, whereas you went for page_cgroup lock nested inside lruvec lock
in your lrucare patch.
I couldn't find an imperative reason why they should be one way round or
the other, so I tried hard to stick with your ordering, and it did work
(in this 6/10). But then I couldn't work out how to get rid of the
overheads added in doing it this way round, so swapped them back.
>
> Hmm.... How about adding NR_ISOLATED counter into lruvec ?
>
> Then, we can delay freeing lruvec until all conunters goes down to zero.
> as...
>
> bool we_can_free_lruvec = true;
>
> lock_lruvec(lruvec->lock);
> for_each_lru_lruvec(lru)
> if (!list_empty(&lruvec->lru[lru]))
> we_can_free_lruvec = false;
> if (lruvec->nr_isolated)
> we_can_free_lruvec = false;
> unlock_lruvec(lruvec)
> if (we_can_free_lruvec)
> kfree(lruvec);
>
> If compaction, lumpy reclaim free a page taken from LRU,
> it knows what it does and can decrement lruvec->nr_isolated properly
> (it seems zone's NR_ISOLATED is decremented at putback.)
At the moment I'm thinking that what we end up with by 9/10 is
better than adding such a refcount. But I'm not entirely happy with
mem_cgroup_reset_uncharged_to_root (it adds a further page_cgroup
lookup just after I got rid of some others), and need yet to think
about the race which Konstantin posits, so all options remain open.
Hugh
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next prev parent reply other threads:[~2012-02-21 23:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-20 23:26 [PATCH 0/10] mm/memcg: per-memcg per-zone lru locking Hugh Dickins
2012-02-20 23:28 ` [PATCH 1/10] mm/memcg: scanning_global_lru means mem_cgroup_disabled Hugh Dickins
2012-02-21 8:03 ` KAMEZAWA Hiroyuki
2012-02-20 23:29 ` [PATCH 2/10] mm/memcg: move reclaim_stat into lruvec Hugh Dickins
2012-02-21 8:05 ` KAMEZAWA Hiroyuki
2012-02-20 23:30 ` [PATCH 3/10] mm/memcg: add zone pointer " Hugh Dickins
2012-02-21 8:08 ` KAMEZAWA Hiroyuki
2012-02-20 23:32 ` [PATCH 4/10] mm/memcg: apply add/del_page to lruvec Hugh Dickins
2012-02-21 8:20 ` KAMEZAWA Hiroyuki
2012-02-21 22:25 ` Hugh Dickins
2012-02-20 23:33 ` [PATCH 5/10] mm/memcg: introduce page_relock_lruvec Hugh Dickins
2012-02-21 8:38 ` KAMEZAWA Hiroyuki
2012-02-21 22:36 ` Hugh Dickins
2012-02-20 23:34 ` [PATCH 6/10] mm/memcg: take care over pc->mem_cgroup Hugh Dickins
2012-02-21 5:55 ` Konstantin Khlebnikov
2012-02-21 19:37 ` Hugh Dickins
2012-02-21 20:40 ` Konstantin Khlebnikov
2012-02-21 22:05 ` Hugh Dickins
2012-02-21 6:05 ` Konstantin Khlebnikov
2012-02-21 20:00 ` Hugh Dickins
2012-02-21 9:13 ` KAMEZAWA Hiroyuki
2012-02-21 23:03 ` Hugh Dickins [this message]
2012-02-22 4:05 ` Konstantin Khlebnikov
2012-02-20 23:35 ` [PATCH 7/10] mm/memcg: remove mem_cgroup_reset_owner Hugh Dickins
2012-02-21 9:17 ` KAMEZAWA Hiroyuki
2012-02-20 23:36 ` [PATCH 8/10] mm/memcg: nest lru_lock inside page_cgroup lock Hugh Dickins
2012-02-21 9:48 ` KAMEZAWA Hiroyuki
2012-02-20 23:38 ` [PATCH 9/10] mm/memcg: move lru_lock into lruvec Hugh Dickins
2012-02-21 7:08 ` Konstantin Khlebnikov
2012-02-21 20:12 ` Hugh Dickins
2012-02-21 21:35 ` Konstantin Khlebnikov
2012-02-21 22:12 ` Hugh Dickins
2012-02-22 3:43 ` Konstantin Khlebnikov
2012-02-22 6:09 ` Hugh Dickins
2012-02-23 14:21 ` Konstantin Khlebnikov
2012-02-20 23:39 ` [PATCH 10/10] mm/memcg: per-memcg per-zone lru locking Hugh Dickins
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