Re: [REVIEW] Re: Compression of full-page-writes - Mailing list pgsql-hackers

Hello,

>It'd be interesting to check avg cpu usage as well

I have collected average CPU utilization numbers by collecting sar output at interval of 10 seconds  for following benchmark:

Server specifications:
Processors:Intel® Xeon ® Processor E5-2650 (2 GHz, 8C/16T, 20 MB) * 2 nos
RAM: 32GB
Disk : 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

Benchmark:

Scale : 16
Command  :java JR  /home/postgres/jdbcrunner-1.2/scripts/tpcc.js  -sleepTime 550,250,250,200,200

Warmup time          : 1 sec
Measurement time     : 900 sec
Number of tx types   : 5
Number of agents     : 16
Connection pool size : 16
Statement cache size : 40
Auto commit          : false

Checkpoint segments:1024
Checkpoint timeout:5 mins

Average % of CPU utilization at user level for multiple blocks compression:

Compression Off  =  3.34133

Snappy = 3.41044

LZ4  = 3.59556

 Pglz = 3.66422

The numbers show the average CPU utilization is in the following order pglz > LZ4 > Snappy > No compression 

Attached is the graph which gives plot of % CPU utilization versus time elapsed for each of the compression algorithms.

Also, the overall CPU utilization during tests is very low i.e below 10% . CPU remained idle for large(~90) percentage of time. I will repeat the above tests with high load on CPU and using the benchmark given by Fujii-san and post the results. 

 

Thank you,

On Wed, Aug 27, 2014 at 9:16 PM, Arthur Silva <arthurprs@gmail.com> wrote:

Em 26/08/2014 09:16, "Fujii Masao" <masao.fujii@gmail.com> escreveu:

>
> On Tue, Aug 19, 2014 at 6:37 PM, Rahila Syed <rahilasyed90@gmail.com> wrote:
> > Hello,
> > Thank you for comments.
> >
> >>Could you tell me where the patch for "single block in one run" is?
> > Please find attached patch for single block compression in one run.
>
> Thanks! I ran the benchmark using pgbench and compared the results.
> I'd like to share the results.
>
> [RESULT]
> Amount of WAL generated during the benchmark. Unit is MB.
>
>                 Multiple                Single
>     off            202.0                201.5
>     on            6051.0                6053.0
>     pglz            3543.0                3567.0
>     lz4            3344.0                3485.0
>     snappy            3354.0                3449.5
>
> Latency average during the benchmark. Unit is ms.
>
>                 Multiple                Single
>     off            19.1                19.0
>     on            55.3                57.3
>     pglz            45.0                45.9
>     lz4            44.2                44.7
>     snappy            43.4                43.3
>
> These results show that FPW compression is really helpful for decreasing
> the WAL volume and improving the performance.
>
> The compression ratio by lz4 or snappy is better than that by pglz. But
> it's difficult to conclude which lz4 or snappy is best, according to these
> results.
>
> ISTM that compression-of-multiple-pages-at-a-time approach can compress
> WAL more than compression-of-single-... does.
>
> [HOW TO BENCHMARK]
> Create pgbench database with scall factor 1000.
>
> Change the data type of the column "filler" on each pgbench table
> from CHAR(n) to TEXT, and fill the data with the result of pgcrypto's
> gen_random_uuid() in order to avoid empty column, e.g.,
>
>  alter table pgbench_accounts alter column filler type text using
> gen_random_uuid()::text
>
> After creating the test database, run the pgbench as follows. The
> number of transactions executed during benchmark is almost same
> between each benchmark because -R option is used.
>
>   pgbench -c 64 -j 64 -r -R 400 -T 900 -M prepared
>
> checkpoint_timeout is 5min, so it's expected that checkpoint was
> executed at least two times during the benchmark.
>
> Regards,
>
> --
> Fujii Masao
>
>

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It'd be interesting to check avg cpu usage as well.