From: Alok Mooley <rangdi@yahoo.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, 4 Feb 2004 21:07:30 -0800 (PST) [thread overview]
Message-ID: <20040205050730.40649.qmail@web9708.mail.yahoo.com> (raw)
In-Reply-To: <Pine.LNX.4.53.0402041427270.2947@chaos>
--- "Richard B. Johnson" <root@chaos.analogic.com>
wrote:
> All "blocks" are the same size, i.e., PAGE_SIZE.
> When RAM
> is tight the content of a page is written to the
> swap-file
> according to a least-recently-used protocol. This
> frees
> a page. Pages are allocated to a process only one
> page at
> a time. This prevents some hog from grabbing all the
> memory
> in the machine. Memory allocation and physical page
> allocation
> are two different things, I can malloc() a gigabyte
> of RAM on
> a machine. It only gets allocated when an attempt is
> made
> to access a page.
Only userspace processes are allocated pages via
page-faults, i.e., one page at a time. Processes
running in kernel mode can request higher order blocks
(8K,16K...4M, which are 2 pages,4 pages...1024 pages
respectively) from the buddy allocator directly. If
external fragmentation is rampant, requests for these
higher order blocks may fail. The defragmentation
utility intends to provide a faster option for higher
order block formation before swapping (which is the
last alternative). By the way,
malloc finally takes memory from the buddy allocator
itself (by page-faults), & the defragmenter is out to
reduce the external fragmentation caused by the buddy
allocator. Swapping ofcourse cannot be completely
avoided if the machine is genuinely short of memory.
Defragmentation may now sound better than needless
swapping or memory allocation failures, not just
another cpu hog!
Regards,
Alok
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next prev parent reply other threads:[~2004-02-05 5:07 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 [this message]
2004-02-05 19:03 ` Pavel Machek
2004-02-04 19:35 ` Dave McCracken
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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