Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile

On Thu, May 31, 2012 at 11:23 AM, Sergey Koposov <koposov(at)ast(dot)cam(dot)ac(dot)uk> wrote:
> On Thu, 31 May 2012, Robert Haas wrote:
>>
>> Thanks.  How did you generate this perf report?  It's cool, because I
>> haven't figured out how to make perf generate a report that is easily
>> email-able, and it seems you have.
>
> I did pretty much what you have said, e.g.
> attached it to running process by
> perf record -g -p PID
> and then
> perf report -g  > output

Ah, interesting. I never tried sending the output to a file.

> And postgresql was compiled with cflags=-g
>>
>> The only trouble is that there's no call stack information here for
>> s_lock or PinBuffer, which is what I really want.  It seems to have
>> spit out call stack information only for the kernel functions, and not
>> for user functions.
>
> Yes, I forgot to clean the old binaries when recompiled with cflags=-g.
> So not it is fixed. I attach the updated perf report (i.e. the first 10000
> lines of it to reduce the  file size).

Oh, ho. So from this we can see that the problem is that we're
getting huge amounts of spinlock contention when pinning and unpinning
index pages.

It would be nice to have a self-contained reproducible test case for
this, so that we could experiment with it on other systems.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company