From: Christoph Lameter <clameter@sgi.com>
To: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: linux-mm <linux-mm@kvack.org>, Andi Kleen <ak@suse.de>,
Eric Whitney <eric.whitney@hp.com>
Subject: Re: [PATCH/RFC]
Date: Thu, 20 Apr 2006 16:51:12 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0604201644350.19049@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <1145565435.5214.31.camel@localhost.localdomain>
On Thu, 20 Apr 2006, Lee Schermerhorn wrote:
> Basic "problem": currently [2.6.17-rc1], file mmap()ed SHARED
> do not follow policy applied to the mapped regions. Instead,
> shared file backed pages are allocated using the allocating
> tasks' task policy. This is inconsistent with the way that anon
> and shmem pages are handled.
You mean pages generated while writing to an MMAP_PRIVATE area follow
policy (these are anonymous pages). Not that the pags from the file follow
policy right?
> One reason for this is that down where pages are allocated for
> file backed pages, the faulting (mm, vma, address) are not
> available to compute the policy. However, we do have the inode
> [via the address space] and file index/offset available. If the
> applicable policy could be determined from just this info, the
> vma and address would not be required.
Processes may set individual policies per file. If you do this then there
will be overhead generated through a need for these shared policy
structures. It seems then that this shared policy has the same semantics
as shmem? Exists after processes have terminated?
> Cursory testing with memtoy for shm segments, shared and privately
> mapped files; single task and 2 tasks mmap()ing same file. When
> the file is mmap()ed shared, either task's policy changes are seen
> by both tasks. When one maps shared and the other private, the
> private mapper's policies apply only to its mapping.
Again we are talking about private pages in the sense of the anonymous
pages generated by writing to a private mapping?
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parent reply other threads:[~2006-04-20 23:51 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
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