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Re: stalled 'sync' on ext3+quota over drbd



On Wed, 2004-03-31 at 17:49, Stephen C. Tweedie wrote:

> > I'd be happy to provide more information but so far I cannot decide
> > where to look...  Should I learn to use "kernel profiling"?
> 
> Sound like it.  You've got two choices --- the simple "readprofile"
> (boot with profile=2), or set up an oprofile kernel.  For complex
> user/kernel interactions oprofile can be really helpful, but for
> something that's simply stuck in the kernel, readprofile is fine.

OK, this is readprofile output of sync(1).  To reproduce the situation,
I did a lot of copying of data and in parallel, setqouta for a few
thousands of group ids.  After this kind of activity, sync becomes slow
(in my case it took a couple of minutes.  It will take much more after
more activity).

$ readprofile -m /isolinux/System.map |sort -n|tail -20
    11 zap_pte_range                              0.0220
    13 system_call                                0.2321
    14 do_wp_page                                 0.0182
    19 __find_get_page                            0.2375
    35 __constant_memcpy                          0.1287
    35 ext3_group_sparse                          0.1683
    47 .text.lock.tty_io                          0.1196
    70 dqget                                      0.1326
    76 .text.lock.inode                           0.3028
    89 do_page_fault                              0.0668
    97 .text.lock.namei                           0.0820
   105 .text.lock.read_write                      0.9052
   138 .text.lock.attr                            2.1562
   202 .text.lock.inode                           0.3033
   388 .text.lock.ioctl                          10.7778
   445 .text.lock.exit                            1.5188
  1283 default_idle                              16.0375
  2942 .text.lock.sched                           7.8245
  4414 vfs_quota_sync                            11.0350
 10775 total                                      0.0060

Does it help?  Tell me what to do next.

Eugene

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