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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