Re: [WIP] Performance Improvement by reducing WAL for Update Operation

From: Bruce Momjian [mailto:bruce@momjian.us] 
Sent: Friday, August 24, 2012 2:12 AM
On Wed, Aug 22, 2012 at 07:38:33PM +0530, Amit Kapila wrote:
>> I had made sure no full_page_write happens by making checkpoint interval
and
>> checkpoints segments  longer.
>> 
>  
> 
>> Original code - 1.8G    Modified code - 1.1G  Diff - 63% reduction,
incase of
>> fill factor 100.
>> Original code - 1.6G    Modified code - 1.1G  Diff - 45% reduction,
incase of
>> fill factor 80.
> 
>  
> 
>> I am still in process of collecting synchronous commit mode on data.

> Wow, that sounds promising. Thanks you.

Right now I am collecting the data for Synchronous_commit =on mode; My
initial observation is that
incase fsync is off, the results are good(around 50% perf improvement). 
However if fsync is on, the performance results fall down to 3~5%. I am not
sure even if the data for I/O is reduced, 
Still why there is no big performance gain as in case of Synchronous_commit
= off or when fsync is off.

I am trying with different methods of wal_sync_method parameter and by
setting some value of commit_delay as suggested by Peter Geoghegan in one of
his mails.

Please suggest me if anyone has any thoughts on what kind of parameter's are
best for such a use case or let me know if I am missing anything and such
kind of performance improvement can only improve performance for fsync =off
case.

With Regards,
Amit Kapila.