From: Hugh Dickins <hughd@google.com>
To: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ying Han <yinghan@google.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 9/10] mm/memcg: move lru_lock into lruvec
Date: Tue, 21 Feb 2012 12:12:58 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.00.1202211205280.1858@eggly.anvils> (raw)
In-Reply-To: <4F434300.3080001@openvz.org>
On Tue, 21 Feb 2012, Konstantin Khlebnikov wrote:
>
> On lumpy/compaction isolate you do:
>
> if (!PageLRU(page))
> continue
>
> __isolate_lru_page()
>
> page_relock_rcu_vec()
> rcu_read_lock()
> rcu_dereference()...
> spin_lock()...
> rcu_read_unlock()
>
> You protect page_relock_rcu_vec with switching pointers back to root.
>
> I do:
>
> catch_page_lru()
> rcu_read_lock()
> if (!PageLRU(page))
> return false
> rcu_dereference()...
> spin_lock()...
> rcu_read_unlock()
> if (PageLRU())
> return true
> if true
> __isolate_lru_page()
>
> I protect my catch_page_lruvec() with PageLRU() under single rcu-interval
> with locking.
> Thus my code is better, because it not requires switching pointers back to
> root memcg.
That sounds much better, yes - if it does work reliably.
I'll have to come back to think about your locking later too;
or maybe that's exactly where I need to look, when investigating
the mm_inline.h:41 BUG.
But at first sight, I have to say I'm very suspicious: I've never found
PageLRU a good enough test for whether we need such a lock, because of
races with those pages on percpu lruvec about to be put on the lru.
But maybe once I look closer, I'll find that's handled by your changes
away from lruvec; though I'd have thought the same issue exists,
independent of whether the pending pages are in vector or list.
Hugh
>
> Meanwhile after seeing your patches, I realized that this rcu-protection is
> required only for lock-by-pfn in lumpy/compaction isolation.
> Thus my locking should be simplified and optimized.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-02-21 20:13 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
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 [this message]
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
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=alpine.LSU.2.00.1202211205280.1858@eggly.anvils \
--to=hughd@google.com \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=khlebnikov@openvz.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=yinghan@google.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