Re: [REVIEW] Re: Compression of full-page-writes

Em 26/08/2014 09:16, "Fujii Masao" <masao(dot)fujii(at)gmail(dot)com> escreveu:
>
> On Tue, Aug 19, 2014 at 6:37 PM, Rahila Syed <rahilasyed90(at)gmail(dot)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.