Re: Performance Improvement by reducing WAL for Update Operation

On 02/05/2013 11:53 PM, Amit Kapila wrote:
>> Performance data for the patch is attached with this mail.
>> Conclusions from the readings (these are same as my previous patch):
>>
>> 1. With orignal pgbench there is a max 7% WAL reduction with not much
>> performance difference.
>> 2. With 250 record pgbench there is a max wal reduction of 35% with not
>> much performance difference.
>> 3. With 500 and above record size in pgbench there is an improvement in
>> the performance and wal reduction both.
>>
>> If the record size increases there is a gain in performance and wal
>> size is reduced as well.
>>
>> Performance data for synchronous_commit = on is under progress, I shall
>> post it once it is done.
>> I am expecting it to be same as previous.
> Please find the performance readings for synchronous_commit = on.
>
> Each run is taken for 20 min.
>
> Conclusions from the readings with synchronous commit on mode:
>
> 1. With orignal pgbench there is a max 2% WAL reduction with not much
> performance difference.
> 2. With 500 record pgbench there is a max wal reduction of 3% with not much
> performance difference.
> 3. With 1800 record size in pgbench there is both an improvement in the
> performance (approx 3%) as well as wal reduction (44%).
>
> If the record size increases there is a very good reduction in WAL size.

The stats look fairly sane. I'm a little concerned about the apparent
trend of falling TPS in the patched vs original tests for the 1-client
test as record size increases, but it's only 0.0%->0.2%->0.4%, and the
0.4% case made other config changes too. Nonetheless, it might be wise
to check with really big records and see if the trend continues.

--
Craig Ringer http://www.2ndQuadrant.com/
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