Re: Performance Improvement by reducing WAL for Update Operation

On Friday, January 11, 2013 11:12 PM Simon Riggs wrote:
On 11 January 2013 17:30, Amit kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> On Friday, January 11, 2013 7:59 PM Alvaro Herrera wrote:
> Simon Riggs wrote:
>> On 28 December 2012 10:21, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>
>
>>> I was also worried about the high variance in the results. Those
>>> averages look rather meaningless. Which would be okay, I think, because
>>> it'd mean that performance-wise the patch is a wash,
>
>> For larger tuple sizes (>1000 && < 1800), the performance gain will be good.
>> Please refer performance results by me and Kyotaro-san in below links:
>
>> http://archives.postgresql.org/message-id/6C0B27F7206C9E4CA54AE035729E9C383BEAAE32(at)szxeml509-mbx<http://archives.postgresql.org/message-id/6C0B27F7206C9E4CA54AE035729E9C383BEAAE32%28at%29szxeml509-mbx>
>> http://archives.postgresql.org/message-id/20121228(dot)170748(dot)90887322(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp<http://archives.postgresql.org/message-id/20121228%28dot%29170748%28dot%2990887322%28dot%29horiguchi%28dot%29kyotaro%28at%29lab%28dot%29ntt%28dot%29co%28dot%29jp>

>AFAICS your tests are badly variable, but as Alvaro says, they aren't
>accurate enough to tell there's a regression.

By running performance scenario in suse 11 board, the readings are not varying much except 8 threads, as i feel my board is a 4 core machine.

Performance readings are attached for original, 256, 512, 1000 and 1800 size of records.

Conclusions from the readings:

1. With orignal pgbench there is a max 9% WAL reduction with not much performance difference.
2. With 250 record pgbench there is a max wal reduction of 30% 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.

With Regards,

Amit Kapila.