Re: XFS filesystem performance drop in kernels 2.6.16+

["Igor A. Valcov" <viaprog@gmail.com>]

Below is a simplified version of the test program, and results of
testing different kernels/filesystems/mount options. The results are a
little different from the ones described in the initial post (this
time performance decreased "only" 2 times), but the general tendency
is clearly the same.


============ 2.6.19-rc5-git2 ============

mount -t xfs -o noatime,barrier /dev/sdc1 /mnt/disc

real    16m40.516s
user    0m17.989s
sys    9m36.320s

mount -t xfs -o noatime,nobarrier /dev/sdc1 /mnt/disc

real    15m40.212s
user    0m17.549s
sys    9m29.692s

mount -t ext3 -o noatime /dev/sdc1 /mnt/disc

real    49m44.728s
user    0m27.678s
sys    14m15.689s

============ 2.6.14.6 ============

mount -t xfs -o noatime /dev/sdc1 /mnt/disc

real    9m58.974s
user    0m17.373s
sys    8m4.850s

mount -t ext3 -o noatime /dev/sdc1 /mnt/disc

real    49m7.526s
user    0m26.278s
sys    12m37.627s

========================================

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define __BYTES        8192
#define __FILES        1000

char    buf [__BYTES];

int main ()
{
   char    fname [1024];
   int        nFiles [__FILES];
   int     f, i;

   /* Fill buf */
   for (i = 0; i < __BYTES; i++)
       buf [i] = i % 128;

   /* Create and open files */
   for (f = 0; f < __FILES; f++) {
       sprintf (fname, "/mnt/disc/storage/file-%d", f);
       nFiles [f] = open (fname, O_WRONLY | O_CREAT | O_TRUNC, 0644);
   }

   for (i = 0; i < 262144; i++) {
       /* Write data to a big file */
       write (nFiles [0], buf, __BYTES);

       /* Write data to small files */
       for (f = 1; f < __FILES; f++)
           write (nFiles [f], &f, sizeof (f));
   }

   for (f = 0; f < __FILES; f++) {
       fsync (nFiles [f]);
       close (nFiles [f]);
   }

   return 0;
}

========================================

--
Igor A. Valcov
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