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pgbench: spike in pgbench results(graphs) while testing pg_hint_plan performance - Mailing list pgsql-performance

From Sachin D. Bhosale-Kotwal
Subject pgbench: spike in pgbench results(graphs) while testing pg_hint_plan performance
Date
Msg-id CA+N_YAdDUXkzX9Z5p0G7An_f-=gc8p2ePJe4_aDijWAFQzwYWQ@mail.gmail.com
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Responses Re: pgbench: spike in pgbench results(graphs) while testing pg_hint_plan performance  (Greg Smith <greg@2ndQuadrant.com>)
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Hello,

I am testing performance of postgresql application using pgbench.
I am getting spike in results(graphs) as shown in attached graph due to throughput drop at that time.
pgbench  itself doing checkpoint on server (where queries are running) before and after test starts.
pgbench is running on separate client machine.
actual queries are running on separate server machine.

Test configurations:
test duration is 5 minutes
numbers clients are 120
scale is 100
query mode is prepared
only select queries are used.

result graph: see attachment tps.png

spike is at 12:09:14

My Observatios:

In vmstat, sar , iostat, top  logs i found that at the time of spike there is more iowait on pgbench-client.
there is similar iowait at another timestamp present but there is no spike.
So i am not getting why spike occure at 12:09:14 only.
If anyone find solution of this problem please reply.
Also i am working to get context switches at the time of spike occurred.

Please reply if any clue.

------------------------------------------------------------------------------
pgbench Client machine configuration:
Hardware and OS specifications for pgbench-client

Parameter:Value
Processor: INTEL XEON  (E5645) 2.40GHz*2 PROCESSOR
Total Cores:12. 6 cores per processor
RAM: 8 GB RAM (4GB*2)
HDD: 300GB*2 SAS HDD. RAID 1 configured. So only one disk in use at a time. 2nd disk is used for mirroring. 

Operating  System:GNU/Linux
Red  Hat  release: Red Hat Enterprise Linux Server release 6.3 (Santiago)

Server machine configuration and environment setup:
Hardware and OS specifications for server:

Parameter: Value
Processors: Xeon E5-2650 Processor Kit , Intel® Xeon ® Processor E5-2650 (2 GHz, 8C/16T, 20 MB) * 2 nos (Part No. N8101-549F)
RAM: 32GB DDR3-1600 REG Memory Kit , 8x 4GB Registered ECC DIMM, DDR3L-1600(PC3L-12800) (Part No. N8102-469F)
HDD: 450GB 10K Hot Plug 2.5-inch SAS HDD * 8 nos 1 x 450 GB SAS HDD, 2.5-inch, 6Gb/s, 10,000 rpm (Part No. N8150-322)

Operating  System: GNU/Linux
Red  Hat  release: Red Hat Enterprise Linux Server release 6.3 (Santiago)



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