Mailinglist Archive: opensuse (1239 mails)

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Re: [opensuse] XFS and openSUSE 12.1


Roger Oberholtzer <roger@xxxxxx> wrote:

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.

So, I am curious if anyone has seen performance issues like this with
XFS on openSUSE 12.1.


The xfs mailing list has very knowledgable people on it and they address
performance questions routinely so you can ask there.

xfs@xxxxxxxxxxx (I think)

Separately have you tried all of the elevators? I think there are only 3 or 4.

Last, but not least, have you tried O_DIRECT in your open call. That can have
a major impact since it disables kernel buffering.

Greg
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