Thread: [OT] linux 3.10 kernel will improve ipc,sysv semaphore scalability

[OT] linux 3.10 kernel will improve ipc,sysv semaphore scalability

From
Andrea Suisani
Date:
Hi all,

Just to let the community know that probably Linux kernel 3.10
will include some work to make sysv semaphore code more scalable.
Since Postgres use this kernel features I've thought to post it
here just for the sake of sharing a good news:

The thread where Rik van Riel posts the v3 patch series:

http://thread.gmane.org/gmane.linux.kernel/1460761

Here http://thread.gmane.org/gmane.linux.kernel/1460761/focus=1461794
Davidlohr Bueso (patches co-author) post an interesting results
comparing multiple runs of "[his] Oracle Swingbench DSS" workload.
Reported here for brevity:

TPS:
100 users: 1257.21 (vanilla)    2805.06 (v3 patchset)
400 users: 1437.57 (vanilla)    2664.67 (v3 patchset)
800 users: 1236.89 (vanilla)    2750.73 (v3 patchset)

ipc lock contention:
100 users:  8,74%  (vanilla)    3.17% (v3 patchset)
400 users:  21,86% (vanilla)    5.23% (v3 patchset)
800 users   84,35% (vanilla)    7.39% (v3 patchset)

as soon as I've a spare server to play with and a little
of time I will give it a spin.

Andrea







Re: [OT] linux 3.10 kernel will improve ipc,sysv semaphore scalability

From
Shaun Thomas
Date:
On 03/26/2013 08:04 AM, Andrea Suisani wrote:

> TPS:
> 100 users: 1257.21 (vanilla)    2805.06 (v3 patchset)
> 400 users: 1437.57 (vanilla)    2664.67 (v3 patchset)
> 800 users: 1236.89 (vanilla)    2750.73 (v3 patchset)

Wow, I like the look of that. I wonder how this reacts with disabled
autogrouping and increasing sched_migration_cost. If the completely fair
scheduler has less locking contention with this patch-set, those tweaks
may not even be necessary. I need to see if I can find a system to test on.

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-676-8870
sthomas@optionshouse.com

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Re: [OT] linux 3.10 kernel will improve ipc,sysv semaphore scalability

From
Andrea Suisani
Date:
Hi

On 03/26/2013 07:59 PM, Shaun Thomas wrote:
> On 03/26/2013 08:04 AM, Andrea Suisani wrote:
>
>> TPS:
>> 100 users: 1257.21 (vanilla)    2805.06 (v3 patchset)
>> 400 users: 1437.57 (vanilla)    2664.67 (v3 patchset)
>> 800 users: 1236.89 (vanilla)    2750.73 (v3 patchset)
>
> Wow, I like the look of that.

Me too.

> I wonder how this reacts with disabled autogrouping and increasing
> sched_migration_cost. If the completely fair scheduler has less locking
 > contention with this patch-set, those tweaks may not even be necessary.
 > I need to see if I can find a system to test on.

Yep, I'm eager to test it too, but unfortunately I have
no spare server to use. Probably early next I'll test it
on my workstation.

Andrea




Re: [OT] linux 3.10 kernel will improve ipc,sysv semaphore scalability

From
Andrea Suisani
Date:
Hi all,

On 03/26/2013 07:59 PM, Shaun Thomas wrote:
> On 03/26/2013 08:04 AM, Andrea Suisani wrote:
>
>> TPS:
>> 100 users: 1257.21 (vanilla)    2805.06 (v3 patchset)
>> 400 users: 1437.57 (vanilla)    2664.67 (v3 patchset)
>> 800 users: 1236.89 (vanilla)    2750.73 (v3 patchset)
>
> Wow, I like the look of that. I wonder how this reacts with disabled autogrouping and increasing
sched_migration_cost.If the completely fair scheduler has less locking contention with this patch-set, those tweaks may
noteven be necessary. I need to see if I can find a system to test on. 
>


still no time to do proper testing but I just want to inform that the
patchset actually went in the 3.10 first release candidate, as we can see
from git log :)


git log v3.9..v3.10-rc1 --grep="ipc,sem: fine grained locking for semtimedop" -- ipc/sem.c

commit 6062a8dc0517bce23e3c2f7d2fea5e22411269a3
Author: Rik van Riel <riel@surriel.com>
Date: Tue Apr 30 19:15:44 2013 -0700

ipc,sem: fine grained locking for semtimedop

...