Mailinglist Archive: opensuse (1239 mails)

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[opensuse] Re: XFS and openSUSE 12.1
Roger Oberholtzer wrote:
On Tue, 2013-06-04 at 11:26 -0700, Linda Walsh wrote:
Any buffers are filled up very quickly when you write 25 MB/Sec. So
something happening after 30 minutes is probably not related to general
This is where I think you'll benet most by using O_DIRECT in your
open call and either a 2nd thread to handle I/O, or async I/O

By writing to /dev/null instead of a disk you are avoiding the kernel's
disk-io routines as well as the xfs-io routines. I.e. it could be
either one. That's why trying O_DIRECT can help eliminate the kernel's
I/O buffering routines.

I do not think the kernel is the culprit. I think it is the hard disk
itself. We will be trying some higher performance discs.
It sounds like you are seeing the overhead of the buffering
in the kernel.

If you don't like O_DIRECT, you could try giving the kernel
hints with the POSIX calls
I.e. calling
posix_fadvise(tfd, 0, 0, POSIX_FADV_DONTNEED);
on each file descriptor you are writing might

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