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

On Wed, Dec 13, 2017 at 5:57 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Wed, Dec 13, 2017 at 4:30 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> On 2017-12-13 16:02:45 +0900, Masahiko Sawada wrote:
>>> When we add extra blocks on a relation do we access to the disk? I
>>> guess we just call lseek and write and don't access to the disk. If so
>>> the performance degradation regression might not be much.
>>
>> Usually changes in the file size require the filesystem to perform
>> metadata operations, which in turn requires journaling on most
>> FSs. Which'll often result in synchronous disk writes.
>>
>
> Thank you. I understood the reason why this measurement should use two
> different filesystems.
>

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.

Regards,

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