Mailinglist Archive: opensuse (1239 mails)

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Re: [opensuse] Re: XFS and openSUSE 12.1
  • From: Roger Oberholtzer <roger@xxxxxx>
  • Date: Tue, 11 Jun 2013 14:52:36 +0200
  • Message-id: <1370955156.2020.89.camel@acme.pacific>
On Tue, 2013-06-11 at 14:06 +0200, Carlos E. R. wrote:
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On 2013-06-11 14:01, Per Jessen wrote:
Roger Oberholtzer wrote:


Try /proc/sys/vm/drop_caches

from https://www.kernel.org/doc/Documentation/sysctl/vm.txt
---------------------------------------------------------------------


Writing to this will cause the kernel to drop clean caches, dentries and
inodes from memory, causing that memory to become free.

To free pagecache: echo 1 > /proc/sys/vm/drop_caches To free
dentries and inodes: echo 2 > /proc/sys/vm/drop_caches To free
pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches

As this is a non-destructive operation and dirty objects are not
freeable, the user should run `sync' first.
--------------------------------------------------------------------

But

as this empties all, not only the ones he wants, other processes
read/writing to disk will delay. For instance, syslog. Or library
loading. Whatever. :-)

In my strange use, I have only one single writer per disk, no reader. No
files are deleted. Just one growing file (up to 2GB) on a pristine disk.

As a little test, I made a 60 second loop that runs the following each
iteration:

echo 1 > /proc/sys/vm/drop_caches

This results in the cache going away. More interestingly, it seems that
this also results in even write times. There are small variations, which
I expect. But I have yet to see the longer ones. There is no discernible
delay when the command is run. Just less memory given over to cache, and
(fingers crossed) less periodic housekeeping as a result.

Of course, I have been fooled before. Longer tests are needed.



Yours sincerely,

Roger Oberholtzer

Ramböll RST / Systems

Office: Int +46 10-615 60 20
Mobile: Int +46 70-815 1696
roger.oberholtzer@xxxxxxxxxx
________________________________________

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden
www.rambollrst.se


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