<font size=2 face="sans-serif">try </font><br><br><font size=2 face="sans-serif">mmfsadm dump iohist </font><br><br><font size=2 face="sans-serif">gives you a nice approach, on how long
it takes until an IO is processed .. the statistic reports the time it
takes, the IO is done from GPFS <--> to your block devices (including
the path to it) </font><br><br><br><br><div><font size=2 face="sans-serif">Mit freundlichen Gren / Kind regards</font><br><br><font size=2 face="sans-serif"> <br>Olaf Weiser<br> <br>EMEA Storage Competence Center Mainz, German / IBM Systems, Storage Platform,<br>-------------------------------------------------------------------------------------------------------------------------------------------<br>IBM Deutschland<br>IBM Allee 1<br>71139 Ehningen<br>Phone: +49-170-579-44-66<br>E-Mail: olaf.weiser@de.ibm.com<br>-------------------------------------------------------------------------------------------------------------------------------------------<br>IBM Deutschland GmbH / Vorsitzender des Aufsichtsrats: Martin Jetter<br>Geschftsfhrung: Martina Koederitz (Vorsitzende), Susanne Peter, Norbert
Janzen, Dr. Christian Keller, Ivo Koerner, Markus Koerner<br>Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart,
HRB 14562 / WEEE-Reg.-Nr. DE 99369940 </font><br><br><br><br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">Aaron Knister <aaron.s.knister@nasa.gov></font><br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif"><gpfsug-discuss@spectrumscale.org></font><br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">08/29/2016 07:54 PM</font><br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">Re: [gpfsug-discuss]
iowait?</font><br><font size=1 color=#5f5f5f face="sans-serif">Sent by:
</font><font size=1 face="sans-serif">gpfsug-discuss-bounces@spectrumscale.org</font><br><hr noshade><br><br><br><tt><font size=2>Sure, we can and we do use both iostat/sar and collectl
to collect disk <br>utilization on our nsd servers. That doesn't give us insight, though, <br>into any individual client node of which we've got 3500. We do log <br>mmpmon data from each node but that doesn't give us any insight into how
<br>much time is being spent waiting on I/O. Having GPFS report iowait on <br>client nodes would give us this insight.<br><br>On 8/29/16 1:50 PM, Alex Chekholko wrote:<br>> Any reason you can't just use iostat or collectl or any of a number
of<br>> other standards tools to look at disk utilization?<br>><br>> On 08/29/2016 10:33 AM, Aaron Knister wrote:<br>>> Hi Everyone,<br>>><br>>> Would it be easy to have GPFS report iowait values in linux? This
would<br>>> be a huge help for us in determining whether a node's low utilization
is<br>>> due to some issue with the code running on it or if it's blocked
on I/O,<br>>> especially in a historical context.<br>>><br>>> I naively tried on a test system changing schedule() in<br>>> cxiWaitEventWait() on line ~2832 in gpl-linux/cxiSystem.c to this:<br>>><br>>> again:<br>>> /* call the scheduler */<br>>> if ( waitFlags & INTERRUPTIBLE )<br>>> schedule();<br>>> else<br>>> io_schedule();<br>>><br>>> Seems to actually do what I'm after but generally bad things happen
when<br>>> I start pretending I'm a kernel developer.<br>>><br>>> Any thoughts? If I open an RFE would this be something that's
relatively<br>>> easy to implement (not asking for a commitment *to* implement
it, just<br>>> that I'm not asking for something seemingly simple that's actually<br>>> fairly hard to implement)?<br>>><br>>> -Aaron<br>>><br>><br><br>-- <br>Aaron Knister<br>NASA Center for Climate Simulation (Code 606.2)<br>Goddard Space Flight Center<br>(301) 286-2776<br>_______________________________________________<br>gpfsug-discuss mailing list<br>gpfsug-discuss at spectrumscale.org<br></font></tt><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss"><tt><font size=2>http://gpfsug.org/mailman/listinfo/gpfsug-discuss</font></tt></a><tt><font size=2><br><br></font></tt><br></div><BR>