Mailinglist Archive: opensuse (1239 mails)

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Re: [opensuse] XFS and openSUSE 12.1
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Wed, 12 Jun 2013 16:30:58 +0200
  • Message-id: <kpa0n2$crr$1@saturn.local.net>
Andrey Borzenkov wrote:

В Mon, 03 Jun 2013 11:14:07 +0200
Roger Oberholtzer <roger@xxxxxx> пишет:

I am using XFS on a 12.1 system. The system records jpeg data to
large files in real time. We have used XFS for this for a while since
it has as a listed feature that it is well suited to writing
streaming media data. We have used this for quite a while on openSUSE
11.2.

We have developed a new version of this system that collects more
data. What I have found is that the jpeg data is typically written at
the speed I expect. Every once in a while, the write takes 100x
longer. Instead of the expected 80 msecs or so to do the compress and
write, it takes, say, 4 or 5 seconds. I have looked in all the usual
suspect places, and nothing seems to point at anything. For one test,
I wrote to /dev/null instead of the real file, The delays do not
happen. They do seem to be related to actually writing to the
physical disk.

I expect some delay occasionally when disks are physically flushed.
There is buffering in our application to allow this. But 5 seconds is
simply wrong.


BTW this may explain one possible cause:

http://serverfault.com/questions/126413/limit-linux-background-flush-dirty-pages


Very interesting read, I think Roger might well find some help there.



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Per Jessen, Zürich (23.9°C)
http://www.dns24.ch/ - free DNS hosting, made in Switzerland.

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