From: Andi Kleen <andi@firstfloor.org>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Christoph Lameter <cl@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mel@csn.ul.ie>, Wu Fengguang <fengguang.wu@intel.com>,
Jun'ichi Nomura <j-nomura@ce.jp.nec.com>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/9] Hugepage migration (v2)
Date: Wed, 18 Aug 2010 09:46:23 +0200 [thread overview]
Message-ID: <20100818074623.GA6866@basil.fritz.box> (raw)
In-Reply-To: <20100818073234.GA28961@spritzera.linux.bs1.fc.nec.co.jp>
On Wed, Aug 18, 2010 at 04:32:34PM +0900, Naoya Horiguchi wrote:
> On Tue, Aug 17, 2010 at 11:40:08AM +0200, Andi Kleen wrote:
> > > When get_user_pages_fast() is called before try_to_unmap(),
> > > direct I/O code increments refcount on the target page.
> > > Because this refcount is not associated to the mapping,
> > > migration code will find remaining refcounts after try_to_unmap()
> > > unmaps all mappings. Then refcount check decides migration to fail,
> > > so direct I/O is continued safely.
> >
> > This would imply that direct IO can make migration fail arbitarily.
> > Also not good. Should we add some retries, at least for the soft offline
> > case?
>
> Soft offline is kicked from userspace, so the retry logic can be implemented
> in userspace. However, currently we can't distinguish migration failure from
I don't think user space is the right place for retry logic.
It doesn't really have enough information to make a good decision when
to reply.
Also I would consider requiring user space to work around kernel problems like
that bad design.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
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prev parent reply other threads:[~2010-08-18 7:46 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-10 9:27 [PATCH 0/9] Hugepage migration (v2) Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 1/9] HWPOISON, hugetlb: move PG_HWPoison bit check Naoya Horiguchi
2010-08-18 0:18 ` Wu Fengguang
2010-08-19 7:55 ` Naoya Horiguchi
2010-08-19 9:28 ` Wu Fengguang
2010-08-23 9:24 ` Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 2/9] hugetlb: add allocate function for hugepage migration Naoya Horiguchi
2010-08-17 6:51 ` David Rientjes
2010-08-18 3:02 ` Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 3/9] hugetlb: rename hugepage allocation functions Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 4/9] hugetlb: redefine hugepage copy functions Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 5/9] hugetlb: hugepage migration core Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 6/9] HWPOISON, hugetlb: soft offlining for hugepage Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 7/9] HWPOISON, hugetlb: fix unpoison " Naoya Horiguchi
2010-08-10 9:27 ` [PATCH 8/9] page-types.c: fix name of unpoison interface Naoya Horiguchi
2010-08-19 1:24 ` Wu Fengguang
2010-08-10 9:27 ` [PATCH 9/9] hugetlb: add corrupted hugepage counter Naoya Horiguchi
2010-08-19 1:57 ` Wu Fengguang
2010-08-24 3:01 ` Naoya Horiguchi
2010-08-24 3:08 ` Wu Fengguang
2010-08-11 13:09 ` [PATCH 0/9] Hugepage migration (v2) Christoph Lameter
2010-08-12 7:53 ` Naoya Horiguchi
2010-08-12 7:57 ` [RFC] [PATCH 1/4] hugetlb: prepare exclusion control functions for hugepage Naoya Horiguchi
2010-08-12 7:59 ` [RFC] [PATCH 2/4] dio: add page locking for direct I/O Naoya Horiguchi
2010-08-12 13:42 ` Jeff Moyer
2010-08-16 2:07 ` Naoya Horiguchi
2010-08-16 7:21 ` Andi Kleen
2010-08-16 13:20 ` Jeff Moyer
2010-08-17 8:17 ` Naoya Horiguchi
2010-08-17 13:46 ` Jeff Moyer
2010-08-17 14:21 ` Andi Kleen
2010-08-17 16:41 ` Christoph Lameter
2010-08-12 8:00 ` [PATCH 3/4] HWPOISON: replace locking functions into hugepage variants Naoya Horiguchi
2010-08-12 8:00 ` [PATCH 4/4] correct locking functions of hugepage migration routine Naoya Horiguchi
2010-08-13 12:47 ` [PATCH 0/9] Hugepage migration (v2) Christoph Lameter
2010-08-16 9:19 ` Naoya Horiguchi
2010-08-16 12:19 ` Christoph Lameter
2010-08-17 2:37 ` Naoya Horiguchi
2010-08-17 8:18 ` Naoya Horiguchi
2010-08-17 9:40 ` Andi Kleen
2010-08-18 7:32 ` Naoya Horiguchi
2010-08-18 7:46 ` Andi Kleen [this message]
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