Re: 64-bit vs 32-bit performance ... backwards?

Luke

Luke Lonergan schrieb:
> On 6/13/06 2:04 AM, "Sven Geisler" <sgeisler@aeccom.com> wrote:
>> Please find attached a small patch with does apply a change to the
>> x86_64 part also to the i386 part of src/include/storage/s_lock.h.
>> Without this change the performance of PostgreSQL 8.0 was horrible on a
>> Opteron. The effect is smaller with PostgreSQL 8.1.
>
> Can you describe what kinds of tests you ran to check your speed?

I has create a test scenario with parallel client which running mostly
SELECTs on the same tables. I used a sequence of 25 queries using 10
tables. We use the total throughput (queries per second) as result.

>
> Since it's the TAS lock that you are patching, the potential impact is
> diffuse and large: xlog.c, shmem.c, lwlock.c, proc.c, all do significant
> work.

Yes, I know. We had a problem last year with the performance of the
Opteron. We have started the futex patch to resolve the issue. The futex
patch itself did have no effect, but there was a side effect because the
futex patch did use also another assembler sequence. This make a hole
difference on a Opteron. It turned out that removing the lines

cmpb
jne
lock

was the reason why the Opteron runs faster.
I have created a sequence of larger query with following result on
Opteron 875 and PostgreSQL 8.0.3
orignal 8.0.3 => 289 query/time and 10% cpu usage
patched 8.0.3 => 1022 query/time and 45% cpu usage

I has a smaller effect on a XEON MP with EM64T. But this effect wasn't
that huge. There was no effect on classic XEON's.

Cheers
Sven.