Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager - Mailing list pgsql-hackers

On Mon, Dec 18, 2017 at 2:04 PM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> On Sun, Dec 17, 2017 at 12:27 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Thu, Dec 14, 2017 at 5:45 AM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>>> Here is the result.
>>> I've measured the through-put with some cases on my virtual machine.
>>> Each client loads 48k file to each different relations located on
>>> either xfs filesystem or ext4 filesystem, for 30 sec.
>>>
>>> Case 1: COPYs to relations on different filessystems(xfs and ext4) and
>>> N_RELEXTLOCK_ENTS is 1024
>>>
>>> clients = 2, avg = 296.2068
>>> clients = 5, avg = 372.0707
>>> clients = 10, avg = 389.8850
>>> clients = 50, avg = 428.8050
>>>
>>> Case 2: COPYs to relations on different filessystems(xfs and ext4) and
>>> N_RELEXTLOCK_ENTS is 1
>>>
>>> clients = 2, avg = 294.3633
>>> clients = 5, avg = 358.9364
>>> clients = 10, avg = 383.6945
>>> clients = 50, avg = 424.3687
>>>
>>> And the result of current HEAD is following.
>>>
>>> clients = 2, avg = 284.9976
>>> clients = 5, avg = 356.1726
>>> clients = 10, avg = 375.9856
>>> clients = 50, avg = 429.5745
>>>
>>> In case2, the through-put got decreased compare to case 1 but it seems
>>> to be almost same as current HEAD. Because the speed of acquiring and
>>> releasing extension lock got x10 faster than current HEAD as I
>>> mentioned before, the performance degradation may not have gotten
>>> decreased than I expected even in case 2.
>>> Since my machine doesn't have enough resources the result of clients =
>>> 50 might not be a valid result.
>>
>> I have to admit that result is surprising to me.
>>
>
> I think the environment I used for performance measurement did not
> have enough resources. I will do the same benchmark on an another
> environment to see if it was a valid result, and will share it.
>

I did performance measurement on an different environment where has 4
cores and physically separated two disk volumes. Also I've change the
benchmarking so that COPYs load only 300 integer tuples which are not
fit within single page, and changed tables to unlogged tables to
observe the overhead of locking/unlocking relext locks.

Case 1: COPYs to relations on different filessystems(xfs and ext4) and
N_RELEXTLOCK_ENTS is 1024

clients = 1, avg = 3033.8933
clients = 2, avg = 5992.9077
clients = 4, avg = 8055.9515
clients = 8, avg = 8468.9306
clients = 16, avg = 7718.6879

Case 2: COPYs to relations on different filessystems(xfs and ext4) and
N_RELEXTLOCK_ENTS is 1

clients = 1, avg = 3012.4993
clients = 2, avg = 5854.9966
clients = 4, avg = 7380.6082
clients = 8, avg = 7091.8367
clients = 16, avg = 7573.2904

And the result of current HEAD is following.

clients = 1, avg = 2962.2416
clients = 2, avg = 5856.9774
clients = 4, avg = 7561.1376
clients = 8, avg = 7252.0192
clients = 16, avg = 7916.7651

As per the above results, compared with current HEAD the through-put
of case 1 got increased up to 17%. On the other hand, the through-put
of case 2 got decreased 2%~5%.

Regards,

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