Re: lazy vxid locks, v1

On Mon, Jun 13, 2011 at 10:29 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)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
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