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Re: [PERFORM] 9.4 -> 9.5 regression with queries through pgbouncer on RHEL 6 - Mailing list pgsql-hackers

From Vladimir Borodin
Subject Re: [PERFORM] 9.4 -> 9.5 regression with queries through pgbouncer on RHEL 6
Date
Msg-id B8A94724-DD6E-463C-A0BC-4750FF71D69E@simply.name
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10 июня 2016 г., в 1:28, Andres Freund <andres@anarazel.de> написал(а):

Hi,

On 2016-06-02 14:18:26 +0300, Антон Бушмелев wrote:
UP. repeat tests on local vm.. reults are discouraging
OS        PG     TPS AVG latency
Centos 7 9.5.3 23.711023 168.421
Centos 7 9.5.3 26.609271 150.188
Centos 7 9.5.3 25.220044 158.416
Centos 7 9.5.3 25.598977 156.047
Centos 7 9.4.8 278.572191 14.077
Centos 7 9.4.8 247.237755 16.177
Centos 7 9.4.8 240.007524 16.276
Centos 7 9.4.8 237.862238 16.596

Could you provide profiles on 9.4 and 9.5?  Which kernel did you have
enabled? Is /proc/sys/kernel/sched_autogroup_enabled 1 or 0?

I don’t know anything about Anton’s installation. I’m having troubles on RHEL 6 with stock kernel (2.6.32-642.el6.x86_64). I also tried a couple  of non-official kernels (3.10, 3.19) but results didn’t change much.

/proc/sys/kernel/sched_autogroup_enabled doesn’t change the picture in general for 9.5 or 9.6 but improves for 9.4:
root@pgload05g ~ # cat /proc/sys/kernel/sched_autogroup_enabled
0
root@pgload05g ~ # /tmp/run.sh
RHEL 6 9.4 69163 0.925
RHEL 6 9.5 34495 1.855
RHEL 6 9.6 70631 0.906
root@pgload05g ~ # echo 1 >/proc/sys/kernel/sched_autogroup_enabled
root@pgload05g ~ # /tmp/run.sh
RHEL 6 9.4 82242 0.778
RHEL 6 9.5 34100 1.877
RHEL 6 9.6 70599 0.907
root@pgload05g ~ #

For taking perf profiles I’ve recompiled all versions with CFLAGS='-O2 -fno-omit-frame-pointer’ and issued the following command during pgbench runs:
perf record -g --call-graph=dwarf -a -o pg9?_all.data sleep 10

After run:
perf report -g -i pg9?_all.data >/tmp/pg9?_perf_report.txt

The results from pg9?_perf_report.txt are attached. Note that in all cases some events were lost, i.e.:

root@pgload05g ~ # perf report -g -i pg94_all.data >/tmp/pg94_perf_report.txt
Failed to open [vsyscall], continuing without symbols
Warning:
Processed 537137 events and lost 7846 chunks!

Check IO/CPU overload!

root@pgload05g ~ #

The reason for that is overloaded I/O subsystem.



Regards,

Andres


--
May the force be with you…

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