svn commit: r228424 - in head/sys: kern sys

[Florian Smeets]

On 25.01.12 22:59, Andriy Gapon wrote:
> on 24/01/2012 00:53 Florian Smeets said the following:
>> On 11.12.11 22:02, Andriy Gapon wrote:
>>> Author: avg Date: Sun Dec 11 21:02:01 2011 New Revision: 228424 URL:
>>> http://svn.freebsd.org/changeset/base/228424
>>>
>>> Log: panic: add a switch and infrastructure for stopping other CPUs in
>>> SMP case
>>>
> 
>> Hi,
> 
>> Attilio asked me to verify that this commit does not introduce a 
>> performance regression.
> 
> First of all, thank you very much for doing this!
> 
>> The box used to run these tests was a 40 Core 32GB Xeon box (HTT was turned
>> off, so 40 real hardware cores). As benchmark pgbench/PostgreSQL were used,
>> a snapshot of PostgreSQL 9.2 from 16.01.2012 was used as they did a lot of
>> scaling work in 9.2 which improved the numbers quite a lot vs. 9.1. The
>> initial benchmarks were run with a scaling factor of 100 which creates a
>> database work set of ~1.5GB. Max throughput was achieved at 20 Clients.
> 

[mangled ministat removed]

> 
>> At 40 threads the results varied between 43000 - 76500 across reboots. 
>> Attilio suspects that this can be caused by the kernel memory layout 
>> changing under the woods creating cache effects difficult to control, 
>> therefor the scaling factor was reduced to 10 (~150MB work set) and the 
>> numbers got deterministic across reboot.
> 

[mangled ministat removed]

> 
> 
> Is it possible to see ministat's report for the difference between
> 228424-40-sf10 and 228424-40-sf10-cl datasets?
> 

Sure, here we go.

x 228424-40-sf10
+ 228424-40-sf10-cl
+----------------------------------------------------------------------+
|x  + +  +     x      ++x   + x +   +      ++  x   x                  x|
|        |____________________M_A_____________________|                |
|         |______________A__M__________|                               |
+----------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x  10     194093.35     198864.83     196129.36     196214.69     1545.8783
+  10     194288.28     197083.85     195955.26     195733.15     1012.3529
No difference proven at 95.0% confidence

>> The 228424-40-sf10-cl results are with a patch from Attilio [1] which he 
>> will followup on.
> 
> I like the patch already, regardless of how much performance difference it
> produces :-)
> 

Florian

[1] http://people.freebsd.org/~attilio/cachelineunshare.patch

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