Re: Speedup twophase transactions

On 01/11/2016 06:11 PM, Stas Kelvich wrote:
>> On 11 Jan 2016, at 21:40, Jesper Pedersen <jesper.pedersen@redhat.com> wrote:
>> I have done a run with the patch and it looks really great.
>>
>> Attached is the TPS graph - with a 1pc run too - and the perf profile as a flame graph (28C/56T w/ 256Gb mem, 2 x RAID10 SSD).
>>
>
> Thanks for testing and especially for the flame graph. That is somewhat in between the cases that I have tested. On commodity server with dual Xeon (6C each) 2pc speed is about 80% of 1pc speed, but on 60C/120T system that patch didn’t make significant difference because main bottleneck changes from file access to locks on array of running global transactions.
>
> How did you generated names for your PREPARE’s? One funny thing that I’ve spotted that tx rate increased when i was using incrementing counter as GID instead of random string.
>

I'm using https://github.com/jesperpedersen/postgres/tree/pgbench_xa - 
so just the client_id.

The strcmp() in MarkAsPreparing() is under the exclusive lock, so maybe 
that is what you are seeing, as shorter gid's are faster.

> And can you also share flame graph for 1pc workload?
>

Attached with a new 2pc, as the server runs Linux 4.4.0 now, both using 
-F 497 over a 6 min run.

Best regards,
  Jesper