[Bug 62751] INFO: rcu_sched detected stalls on CPUs/tasks: { 3} (detected by 2, t=15107 jiffies, g=270766, c=270765, q=0)

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https://bugzilla.kernel.org/show_bug.cgi?id=62751

Zheng Liu <gnehzuil.liu@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |gnehzuil.liu@gmail.com

--- Comment #10 from Zheng Liu <gnehzuil.liu@gmail.com> ---
Hi Loris,

Sorry for my late reply.  I haven't had a chance to take a closer look at this
problem until now.

(In reply to Loris Luise from comment #8)
> Hello,
> 
> what can I do on my side?

I am not sure whether you use 'delalloc' on your system.  I don't see these
details from the log that you pasted.  So now only I could suggest is that you
can try to turn off the delalloc.  The step is as below:

 % sudo mount -t ext4 -o remount,nodelalloc ${DEV} ${MNT}

After this, it won't track the delayed entry on extent status tree.  So it will
avoid es shrinker to take too much time to scan delayed entries that couldn't
be reclaimed.

Then I will try to reproduce this problem on my sand box and think about how to
improve es shrinker.

Thanks,
- Zheng

> 
> I've done the following modifications:
> 
> 1) Installed latest mainline kernel 3.12
> 
> 2) Replaced SCSI drivers from vmw_pvsci to LSI Logic SAS (mptsas)
> 
> 3) reduced number of CPUs from 8 to 4
> 
> 4) enabled on ESXi (4.1) setting for this machine "CPU Hot add" feature
> 
> The issue is still affecting ths machine... other 2 almost equals machine
> running on this host (same kernel) but with XFS on root are not affected and
> very
> stable.
> 
> I reattached another info file (bug-20131118084007.txt) which contains a lot
> of infos.
> 
> Thanks.

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