On Mon, Jun 13, 2011 at 10:29 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> writes:
>> On 06/12/2011 11:39 PM, Robert Haas wrote:
>>> Profiling reveals that the system spends enormous amounts of CPU time
>>> in s_lock.
>
>> just to reiterate that with numbers - at 160 threads with both patches
>> applied the profile looks like:
>
>> samples % image name symbol name
>> 828794 75.8662 postgres s_lock
>
> Do you know exactly which spinlocks are being contended on here?
> The next few entries
>
>> 51672 4.7300 postgres LWLockAcquire
>> 51145 4.6817 postgres LWLockRelease
>> 17636 1.6144 postgres GetSnapshotData
>
> suggest that it might be the ProcArrayLock as a result of a huge amount
> of snapshot-fetching, but this is very weak evidence for that theory.
I don't know for sure what is happening on Stefan's system, but I did
post the results of some research on this exact topic in my original
post.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
