Re: LWLock optimization for multicore Power machines

On Tue, Feb 7, 2017 at 3:16 PM, Bernd Helmle <mailings(at)oopsware(dot)de> wrote:

> Am Montag, den 06.02.2017, 22:44 +0300 schrieb Alexander Korotkov:
>
> 2. Also could you run each test longer: 3-5 mins, and run them with
> variety of clients count?
>
>
> So here are some other results. I've changed max_connections to 300. The
> bench was prewarmed and run 300s each.
> I could run more benches, if necessary.
>

Thank you very much for benchmarks!

There is clear win of both lwlock-power-1.patch and lwlock-power-3.patch in
comparison to master. Difference between lwlock-power-1.patch and
lwlock-power-3.patch seems to be within the margin of error. But win isn't
as high as I observed earlier. And I wonder why absolute numbers are lower
than in our earlier experiments. We used IBM E880 which is actually two
nodes with interconnect. However interconnect is not fast enough to make
one PostgreSQL instance work on both nodes. Thus, used half of IBM E880
which has 4 sockets and 32 physical cores. While you use IBM E850 which is
really single node with 4 sockets and 48 physical cores. Thus, it seems
that you have lower absolute numbers on more powerful hardware. That makes
me uneasy and I think we probably don't get the best from this hardware.
Just in case, do you use SMT=8?

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company