Re: Speed up Clog Access by increasing CLOG buffers

On Thu, Oct 27, 2016 at 5:14 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>> Thanks Tomas and Dilip for doing detailed performance tests for this
>>> patch. I would like to summarise the performance testing results.
>>>
>>> 1. With update intensive workload, we are seeing gains from 23%~192%
>>> at client count >=64 with group_update patch [1].

this is with unlogged table

>>> 2. With tpc-b pgbench workload (at 1000 scale factor), we are seeing
>>> gains from 12% to ~70% at client count >=64 [2]. Tests are done on
>>> 8-socket intel m/c.

this is with synchronous_commit=off

>>> 3. With pgbench workload (both simple-update and tpc-b at 300 scale
>>> factor), we are seeing gain 10% to > 50% at client count >=64 [3].
>>> Tests are done on 8-socket intel m/c.

this is with synchronous_commit=off

>>> 4. To see why the patch only helps at higher client count, we have
>>> done wait event testing for various workloads [4], [5] and the results
>>> indicate that at lower clients, the waits are mostly due to
>>> transactionid or clientread. At client-counts where contention due to
>>> CLOGControlLock is significant, this patch helps a lot to reduce that
>>> contention. These tests are done on on 8-socket intel m/c and
>>> 4-socket power m/c

these both are with synchronous_commit=off + unlogged table

>>> 5. With pgbench workload (unlogged tables), we are seeing gains from
>>> 15% to > 300% at client count >=72 [6].
>>>
>>
>> It's not entirely clear which of the above tests were done on unlogged
>> tables, and I don't see that in the referenced e-mails. That would be an
>> interesting thing to mention in the summary, I think.
>>
>
> One thing is clear that all results are on either
> synchronous_commit=off or on unlogged tables. I think Dilip can
> answer better which of those are on unlogged and which on
> synchronous_commit=off.

I have mentioned this above under each of your test point..

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com