Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager

On Wed, Nov 22, 2017 at 5:25 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Mon, Nov 20, 2017 at 5:19 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>> Attached updated version patch. I've moved only relation extension
>> locks out of heavy-weight lock as per discussion so far.
>>
>> I've done a write-heavy benchmark on my laptop; loading 24kB data to
>> one table using COPY by 1 client, for 10 seconds. The through-put of
>> patched is 10% better than current HEAD. The result of 5 times is the
>> following.
>>
>> ----- PATCHED -----
>> tps = 178.791515 (excluding connections establishing)
>> tps = 176.522693 (excluding connections establishing)
>> tps = 168.705442 (excluding connections establishing)
>> tps = 158.158009 (excluding connections establishing)
>> tps = 161.145709 (excluding connections establishing)
>>
>> ----- HEAD -----
>> tps = 147.079803 (excluding connections establishing)
>> tps = 149.079540 (excluding connections establishing)
>> tps = 149.082275 (excluding connections establishing)
>> tps = 148.255376 (excluding connections establishing)
>> tps = 145.542552 (excluding connections establishing)
>>
>> Also I've done a micro-benchmark; calling LockRelationForExtension and
>> UnlockRelationForExtension tightly in order to measure the number of
>> lock/unlock cycles per second. The result is,
>> PATCHED = 3.95892e+06 (cycles/sec)
>> HEAD = 1.15284e+06 (cycles/sec)
>> The patched is 3 times faster than current HEAD.
>>
>> Attached updated patch and the function I used for micro-benchmark.
>> Please review it.
>
> That's a nice speed-up.
>
> How about a preliminary patch that asserts that we never take another
> heavyweight lock while holding a relation extension lock?
>

Agreed. Also, since we disallow to holding more than one locks of
different relations at once I'll add an assertion for it as well.

I think we no longer need to pass the lock level to
UnloclRelationForExtension(). Now that relation extension lock will be
simple we can release the lock in the mode that we used to acquire
like LWLock.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center