From: Andi Kleen <andi@firstfloor.org>
To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Huang Ying <ying.huang@intel.com>,
Jin Dongming <jin.dongming@np.css.fujitsu.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] Check whether pages are poisoned before copying
Date: Thu, 17 Mar 2011 07:26:12 +0100 [thread overview]
Message-ID: <20110317062612.GE11094@one.firstfloor.org> (raw)
In-Reply-To: <4D819A2A.8050606@jp.fujitsu.com>
On Thu, Mar 17, 2011 at 02:20:42PM +0900, Hidetoshi Seto wrote:
> (2011/03/17 13:14), Andi Kleen wrote:
> > On Thu, Mar 17, 2011 at 11:32:55AM +0900, Hidetoshi Seto wrote:
> >> So to avoid the above problem, add poison checks for both of 4K pages
> >> and the THP before copying in __collapse_huge_page_copy().
> >
> > I don't think you need the check for the huge page -- it should not be allocated
> > in this case.
>
> Is there no case that the THP is once allocated but poison flag
> is set before copy? Though I know it is one of corner cases,
> having this check for THP is worse than nothing.
There's a theoretical window, but it's only a few instructions.
Probably not worth caring about, especially since you have a similar
window after your check again.
BTW normally I don't recommend to add new poison checks without
doing new studies with page-types if the case is likely and happens
with enough memory.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2011-03-17 6:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-17 2:30 [PATCH 0/4] THP: page collapsing vs. poisoning Hidetoshi Seto
2011-03-17 2:31 ` [PATCH 1/4] Lock the new THP when collapsing pages Hidetoshi Seto
2011-03-17 2:32 ` [PATCH 2/4] Free the collapsed pages after the new THP is mapped Hidetoshi Seto
2011-03-17 2:32 ` [PATCH 3/4] Check whether pages are poisoned before copying Hidetoshi Seto
2011-03-17 4:14 ` Andi Kleen
2011-03-17 5:20 ` Hidetoshi Seto
2011-03-17 6:26 ` Andi Kleen [this message]
2011-03-17 7:43 ` Hidetoshi Seto
2011-03-17 14:04 ` Andrea Arcangeli
2011-03-17 15:25 ` Andi Kleen
2011-03-17 16:12 ` Andrea Arcangeli
2011-03-17 16:27 ` Andi Kleen
2011-03-17 16:47 ` Andrea Arcangeli
2011-03-17 22:55 ` Andi Kleen
2011-03-23 17:26 ` K.Prasad
2011-03-23 17:32 ` Andi Kleen
2011-03-17 15:21 ` Andi Kleen
2011-03-18 5:26 ` Jin Dongming
2011-03-17 2:33 ` [PATCH 4/4] Check whether the new THP is poisoned before it is mapped to APL Hidetoshi Seto
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