From: Johannes Weiner <hannes@cmpxchg.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Petr Holasek <pholasek@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Izik Eidus <izik.eidus@ravellosystems.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 5/7] mm,ksm: swapoff might need to copy
Date: Thu, 21 Feb 2013 09:53:16 -0500 [thread overview]
Message-ID: <20130221145316.GA23767@cmpxchg.org> (raw)
In-Reply-To: <alpine.LNX.2.00.1302210023350.17843@eggly.anvils>
On Thu, Feb 21, 2013 at 12:25:40AM -0800, Hugh Dickins wrote:
> Before establishing that KSM page migration was the cause of my
> WARN_ON_ONCE(page_mapped(page))s, I suspected that they came from the
> lack of a ksm_might_need_to_copy() in swapoff's unuse_pte() - which
> in many respects is equivalent to faulting in a page.
>
> In fact I've never caught that as the cause: but in theory it does
> at least need the KSM_RUN_UNMERGE check in ksm_might_need_to_copy(),
> to avoid bringing a KSM page back in when it's not supposed to be.
Maybe I am mistaken, maybe it was just too obvious to you to mention,
but the main reason for me would be that this can break eviction,
migration, etc. of that page when there is no rmap_item representing
the vma->anon_vma (the cross-anon_vma merge case), no?
> I intended to copy how it's done in do_swap_page(), but have a strong
> aversion to how "swapcache" ends up being used there: rework it with
> "page != swapcache".
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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next prev parent reply other threads:[~2013-02-21 14:53 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-21 8:17 [PATCH 0/7] ksm: responses to NUMA review Hugh Dickins
2013-02-21 8:19 ` [PATCH 1/7] ksm: add some comments Hugh Dickins
2013-02-22 4:26 ` Ric Mason
2013-02-22 20:50 ` Hugh Dickins
2013-02-21 8:20 ` [PATCH 2/7] ksm: treat unstable nid like in stable tree Hugh Dickins
2013-02-22 7:13 ` Ric Mason
2013-02-22 21:03 ` Hugh Dickins
2013-03-01 5:29 ` Ric Mason
2013-03-01 20:03 ` Hugh Dickins
2013-03-02 1:10 ` Ric Mason
2013-03-02 2:57 ` Hugh Dickins
2013-03-06 1:28 ` Will Huck
2013-03-06 4:31 ` Hugh Dickins
2013-03-06 2:37 ` Ric Mason
2013-03-06 5:05 ` Hugh Dickins
2013-03-06 6:58 ` Ric Mason
2013-03-06 10:18 ` Ric Mason
2013-03-07 23:26 ` Ric Mason
2013-02-21 8:22 ` [PATCH 3/7] ksm: shrink 32-bit rmap_item back to 32 bytes Hugh Dickins
2013-02-21 8:23 ` [PATCH 4/7] mm,ksm: FOLL_MIGRATION do migration_entry_wait Hugh Dickins
2013-02-21 8:25 ` [PATCH 5/7] mm,ksm: swapoff might need to copy Hugh Dickins
2013-02-21 14:53 ` Johannes Weiner [this message]
2013-02-22 17:16 ` Hugh Dickins
2013-02-21 8:27 ` [PATCH 6/7] mm: cleanup "swapcache" in do_swap_page Hugh Dickins
2013-02-21 8:29 ` [PATCH 7/7] ksm: allocate roots when needed Hugh Dickins
2013-02-22 3:44 ` [PATCH 0/7] ksm: responses to NUMA review Ric Mason
2013-02-22 20:38 ` Hugh Dickins
2013-02-24 1:39 ` Ric Mason
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