| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: lazy vxid locks, v1 |
| Date: | 2011-06-13 14:29:28 |
| Message-ID: | 16711.1307975368@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
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.
regards, tom lane
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