From: Dave McCracken <dmccr@us.ibm.com>
To: root@chaos.analogic.com
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: Active Memory Defragmentation: Our implementation & problems
Date: Wed, 04 Feb 2004 13:35:54 -0600 [thread overview]
Message-ID: <361730000.1075923354@[10.1.1.5]> (raw)
In-Reply-To: <Pine.LNX.4.53.0402041402310.2722@chaos>
--On Wednesday, February 04, 2004 14:07:52 -0500 "Richard B. Johnson"
<root@chaos.analogic.com> wrote:
> If this is an Intel x86 machine, it is impossible for pages
> to get fragmented in the first place. The hardware allows any
> page, from anywhere in memory, to be concatenated into linear
> virtual address space. Even the kernel address space is virtual.
> The only time you need physically-adjacent pages is if you
> are doing DMA that is more than a page-length at a time. The
> kernel keeps a bunch of those pages around for just that
> purpose.
>
> So, if you are making a "memory defragmenter", it is a CPU time-sink.
Um, wrong answer. When you ask for more than one page from the buddy
allocator (order greater than 0) it always returns physically contiguous
pages.
Also, one of the near-term goals in VM is to be able to allocate and free
large pages from the main memory pools, which requires that something like
order 9 or 10 allocations (based on the architecture) succeed.
Dave McCracken
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next prev parent reply other threads:[~2004-02-04 19:35 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-03 4:46 Alok Mooley
2004-02-03 21:26 ` Dave Hansen
2004-02-03 22:26 ` Martin J. Bligh
2004-02-04 5:09 ` Alok Mooley
2004-02-04 5:24 ` Mike Fedyk
2004-02-04 5:54 ` Dave Hansen
2004-02-04 6:05 ` Martin J. Bligh
2004-02-04 6:22 ` Dave Hansen
2004-02-04 6:29 ` Martin J. Bligh
2004-02-04 6:40 ` Dave Hansen
2004-02-04 7:17 ` Martin J. Bligh
2004-02-04 8:30 ` Andrew Morton
2004-02-04 6:53 ` Doubt about statm_pgd_range patch Arunkumar
2004-02-04 6:57 ` Active Memory Defragmentation: Our implementation & problems IWAMOTO Toshihiro
2004-02-04 7:10 ` Dave Hansen
2004-02-04 7:50 ` IWAMOTO Toshihiro
2004-02-04 10:33 ` Hirokazu Takahashi
2004-02-04 18:33 ` Alok Mooley
2004-02-04 18:46 ` Dave Hansen
2004-02-04 18:54 ` Alok Mooley
2004-02-04 19:07 ` Richard B. Johnson
2004-02-04 19:18 ` Alok Mooley
2004-02-04 19:33 ` Richard B. Johnson
2004-02-05 5:07 ` Alok Mooley
2004-02-05 19:03 ` Pavel Machek
2004-02-04 19:35 ` Dave McCracken [this message]
2004-02-04 21:59 ` Timothy Miller
2004-02-04 23:24 ` Dave Hansen
2004-02-05 16:32 ` Dave McCracken
2004-02-04 19:37 ` Timothy Miller
2004-02-04 19:43 ` Dave Hansen
2004-02-04 19:59 ` Richard B. Johnson
2004-02-04 19:56 ` Dave Hansen
2004-02-05 5:19 ` Alok Mooley
2004-02-04 20:12 Mark_H_Johnson
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