[Gluster-users] [Gluster-devel] 120k context switches on GlsuterFS nodes

[Amar Tumballi]

On Thu, May 18, 2017 at 6:39 PM, Joe Julian <joe at julianfamily.org> wrote:

> On the other hand, tracking that stat between versions with a known test
> sequence may be valuable for watching for performance issues or
> improvements.
>

+1

Once we have nightly build setup, we should take this up. Can do these
after branch out to allow time for fixing major issues if any.

-Amar


>
> On May 17, 2017 10:03:28 PM PDT, Ravishankar N <ravishankar at redhat.com>
> wrote:
>>
>> On 05/17/2017 11:07 PM, Pranith Kumar Karampuri wrote:
>>
>> + gluster-devel
>>
>> On Wed, May 17, 2017 at 10:50 PM, mabi <mabi at protonmail.ch> wrote:
>>
>>> I don't know exactly what kind of context-switches it was but what I
>>> know is that it is the "cs" number under "system" when you run vmstat.
>>>
>> Okay, that could be due to the  syscalls themselves or pre-emptive
>> multitasking in case there aren't enough cpu cores. I think the spike in
>> numbers is due to more users accessing the files at the same time like you
>> observed, translating into more syscalls.  You can try capturing the
>> gluster volume profile info the next time it occurs and co-relate with the
>> cs count. If you don't see any negative performance impact, I think you
>> don't need to be bothered much by the numbers.
>>
>> HTH,
>> Ravi
>>
>>
>>> Also I use the percona linux monitoring template for cacti (
>>> https://www.percona.com/doc/percona-monitoring-plugins/LATE
>>> ST/cacti/linux-templates.html) which monitors context switches too. If
>>> that's of any use interrupts where also quite high during that time with
>>> peaks up to 50k interrupts.
>>>
>>>
>>>
>>> -------- Original Message --------
>>> Subject: Re: [Gluster-users] 120k context switches on GlsuterFS nodes
>>> Local Time: May 17, 2017 2:37 AM
>>> UTC Time: May 17, 2017 12:37 AM
>>> From: ravishankar at redhat.com
>>> To: mabi <mabi at protonmail.ch>, Gluster Users <gluster-users at gluster.org>
>>>
>>>
>>> On 05/16/2017 11:13 PM, mabi wrote:
>>>
>>> Today I even saw up to 400k context switches for around 30 minutes on my
>>> two nodes replica... Does anyone else have so high context switches on
>>> their GlusterFS nodes?
>>>
>>> I am wondering what is "normal" and if I should be worried...
>>>
>>>
>>>
>>>
>>> -------- Original Message --------
>>> Subject: 120k context switches on GlsuterFS nodes
>>> Local Time: May 11, 2017 9:18 PM
>>> UTC Time: May 11, 2017 7:18 PM
>>> From: mabi at protonmail.ch
>>> To: Gluster Users <gluster-users at gluster.org>
>>> <gluster-users at gluster.org>
>>>
>>> Hi,
>>>
>>> Today I noticed that for around 50 minutes my two GlusterFS 3.8.11 nodes
>>> had a very high amount of context switches, around 120k. Usually the
>>> average is more around 1k-2k. So I checked what was happening and there
>>> where just more users accessing (downloading) their files at the same time.
>>> These are directories with typical cloud files, which means files of any
>>> sizes ranging from a few kB to MB and a lot of course.
>>>
>>> Now I never saw such a high number in context switches in my entire life
>>> so I wanted to ask if this is normal or to be expected? I do not find any
>>> signs of errors or warnings in any log files.
>>>
>>>
>>> What context switch are you referring to (syscalls context-switch on the
>>> bricks?) ? How did you measure this?
>>> -Ravi
>>>
>>> My volume is a replicated volume on two nodes with ZFS as filesystem
>>> behind and the volume is mounted using FUSE on the client (the cloud
>>> server). On that cloud server the glusterfs process was using quite a lot
>>> of system CPU but that server (VM) only has 2 vCPUs so maybe I should
>>> increase the number of vCPUs...
>>>
>>> Any ideas or recommendations?
>>>
>>>
>>>
>>> Regards,
>>> M.
>>>
>>>
>>>
>>>
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>>
>> --
>> Pranith
>>
>>
> --
> Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
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-- 
Amar Tumballi (amarts)
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