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

On Thu, Aug 28, 2014 at 12:46 AM, 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.

Yep, but I forgot to collect those info...

Regards,

-- 
Fujii Masao