From: Konstantin Khlebnikov <khlebnikov@openvz.org>
To: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
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 RFC 00/15] mm: memory book keeping and lru_lock splitting
Date: Sat, 18 Feb 2012 10:35:35 +0400 [thread overview]
Message-ID: <4F3F46B7.40100@openvz.org> (raw)
In-Reply-To: <alpine.LSU.2.00.1202171803380.25191@eggly.anvils>
Hugh Dickins wrote:
> On Thu, 16 Feb 2012, Hugh Dickins wrote:
>>
>> Yours are not the only patches I was testing in that tree, I tried to
>> gather several other series which I should be reviewing if I ever have
>> time: Kamezawa-san's page cgroup diet 6, Xiao Guangrong's 4 prio_tree
>> cleanups, your 3 radix_tree changes, your 6 shmem changes, your 4 memcg
>> miscellaneous, and then your 15 books.
>>
>> The tree before your final 15 did well under pressure, until I tried to
>> rmdir one of the cgroups afterwards: then it crashed nastily, I'll have
>> to bisect into that, probably either Kamezawa's or your memcg changes.
>
> So far I haven't succeeded in reproducing that at all: it was real,
> but obviously harder to get than I assumed - indeed, no good reason
> to associate it with any of those patches, might even be in 3.3-rc.
>
> It did involve a NULL pointer dereference in mem_cgroup_page_lruvec(),
> somewhere below compact_zone() - but repercussions were causing the
> stacktrace to scroll offscreen, so I didn't get good details.
There some stupid bugs in my v1 patchset, it shouldn't works at all.
I did not expect that someone will try to use it. I sent it just to discuss.
Most destructive bug is this PageCgroupUsed() below:
+struct book *page_book(struct page *page)
+{
+ struct mem_cgroup_per_zone *mz;
+ struct page_cgroup *pc;
+
+ if (mem_cgroup_disabled())
+ return &page_zone(page)->book;
+
+ pc = lookup_page_cgroup(page);
+ if (!PageCgroupUsed(pc))
+ return &page_zone(page)->book;
+ /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
+ smp_rmb();
+ mz = mem_cgroup_zoneinfo(pc->mem_cgroup,
+ page_to_nid(page), page_zonenum(page));
+ return &mz->book;
+}
Thus after page uncharge I remove page from wrong book, under wrong lock =)
[ as I wrote, updated patchset there: https://github.com/koct9i/linux ]
>
> Hugh
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next prev parent reply other threads:[~2012-02-18 6:35 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-15 22:57 [PATCH RFC 00/15] mm: memory book keeping and lru_lock splitting Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 01/15] mm: rename struct lruvec into struct book Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 02/15] mm: memory bookkeeping core Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 03/15] mm: add book->pages_count Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 04/15] mm: unify inactive_list_is_low() Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 05/15] mm: add book->reclaim_stat Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 06/15] mm: kill struct mem_cgroup_zone Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 07/15] mm: move page-to-book translation upper Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 08/15] mm: introduce book locking primitives Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 09/15] mm: handle book relocks on lumpy reclaim Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 10/15] mm: handle book relocks in compaction Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 11/15] mm: handle book relock in memory controller Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 12/15] mm: optimize books in update_page_reclaim_stat() Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 13/15] mm: optimize books in pagevec_lru_move_fn() Konstantin Khlebnikov
2012-02-15 22:57 ` [PATCH RFC 14/15] mm: optimize putback for 0-order reclaim Konstantin Khlebnikov
2012-02-15 22:58 ` [PATCH RFC 15/15] mm: split zone->lru_lock Konstantin Khlebnikov
2012-02-16 2:04 ` [PATCH RFC 00/15] mm: memory book keeping and lru_lock splitting KAMEZAWA Hiroyuki
2012-02-16 5:43 ` Konstantin Khlebnikov
2012-02-16 8:24 ` KAMEZAWA Hiroyuki
2012-02-16 11:02 ` Konstantin Khlebnikov
2012-02-16 15:54 ` Konstantin Khlebnikov
2012-02-16 23:54 ` KAMEZAWA Hiroyuki
2012-02-18 9:09 ` Konstantin Khlebnikov
2012-02-16 2:37 ` Hugh Dickins
2012-02-16 4:51 ` Konstantin Khlebnikov
2012-02-16 21:37 ` Hugh Dickins
2012-02-17 19:56 ` Konstantin Khlebnikov
2012-02-18 2:13 ` Hugh Dickins
2012-02-18 6:35 ` Konstantin Khlebnikov [this message]
2012-02-18 7:14 ` Hugh Dickins
2012-02-20 0:32 ` KAMEZAWA Hiroyuki
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