From: Dave Hansen <haveblue@us.ibm.com>
To: Valdis.Kletnieks@vt.edu
Cc: Ashwin Rao <ashwin_s_rao@yahoo.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: Atomic operation for physically moving a page
Date: Fri, 18 Jun 2004 19:53:52 -0700 [thread overview]
Message-ID: <1087613632.4921.32.camel@nighthawk> (raw)
In-Reply-To: <200406190103.i5J13WWr010687@turing-police.cc.vt.edu>
On Fri, 2004-06-18 at 18:03, Valdis.Kletnieks@vt.edu wrote:
> On Fri, 18 Jun 2004 17:37:12 PDT, Ashwin Rao <ashwin_s_rao@yahoo.com> said:
> > I want to copy a page from one physical location to
> > another (taking the appr. locks).
>
> At the risk of sounding stupid, what problem are you trying to solve by copying
> a page? Not only (as you note) could the page be referenced by multiple
> processes, it could (conceivably) belong to a kernel slab or something, or be a
> buffer for an in-flight I/O request, or any number of other possibly-racy
> situations.
You also have to make sure that the page is something who's physical
address is allowed to change. Some stuff like DMA buffers, or a part of
a hugetlb page might not even be valid to move.
-- Dave
WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <haveblue@us.ibm.com>
To: Valdis.Kletnieks@vt.edu
Cc: Ashwin Rao <ashwin_s_rao@yahoo.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: Atomic operation for physically moving a page
Date: Fri, 18 Jun 2004 19:53:52 -0700 [thread overview]
Message-ID: <1087613632.4921.32.camel@nighthawk> (raw)
In-Reply-To: <200406190103.i5J13WWr010687@turing-police.cc.vt.edu>
On Fri, 2004-06-18 at 18:03, Valdis.Kletnieks@vt.edu wrote:
> On Fri, 18 Jun 2004 17:37:12 PDT, Ashwin Rao <ashwin_s_rao@yahoo.com> said:
> > I want to copy a page from one physical location to
> > another (taking the appr. locks).
>
> At the risk of sounding stupid, what problem are you trying to solve by copying
> a page? Not only (as you note) could the page be referenced by multiple
> processes, it could (conceivably) belong to a kernel slab or something, or be a
> buffer for an in-flight I/O request, or any number of other possibly-racy
> situations.
You also have to make sure that the page is something who's physical
address is allowed to change. Some stuff like DMA buffers, or a part of
a hugetlb page might not even be valid to move.
-- Dave
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next prev parent reply other threads:[~2004-06-19 2:54 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-19 0:37 Atomic operation for physically moving a page Ashwin Rao
2004-06-19 0:37 ` Ashwin Rao
2004-06-19 1:03 ` Valdis.Kletnieks
2004-06-19 2:53 ` Dave Hansen [this message]
2004-06-19 2:53 ` Dave Hansen
2004-06-19 3:15 ` Atomic operation for physically moving a page (for memory defragmentation) Ashwin Rao
2004-06-19 3:15 ` Ashwin Rao
2004-06-19 3:34 ` Valdis.Kletnieks
2004-06-19 4:25 ` Dave Hansen
2004-06-19 4:25 ` Dave Hansen
2004-06-23 9:04 ` IWAMOTO Toshihiro
2004-06-23 9:04 ` IWAMOTO Toshihiro
2004-06-23 11:59 ` Hirokazu Takahashi
2004-06-23 11:59 ` Hirokazu Takahashi
2004-06-23 20:56 ` Dave Hansen
2004-06-23 20:56 ` Dave Hansen
2004-06-24 7:19 ` IWAMOTO Toshihiro
2004-06-24 7:19 ` IWAMOTO Toshihiro
2004-06-24 11:31 ` Dave Hansen
2004-06-24 11:31 ` Dave Hansen
2004-06-23 10:32 ` Hirokazu Takahashi
2004-06-23 10:32 ` Hirokazu Takahashi
2004-06-19 2:43 ` Atomic operation for physically moving a page Dave Hansen
2004-06-19 2:43 ` Dave Hansen
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