Horton

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

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Thomas Munro <thomas.munro@enterprisedb.com>, Amit Kapila <amit.kapila16@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-12-14T10:45:48Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Allow page lock to conflict among parallel group members.

  2. Allow relation extension lock to conflict among parallel group members.

  3. Add assert to ensure that page locks don't participate in deadlock cycle.

  4. Assert that we don't acquire a heavyweight lock on another object after

  5. Fix unsafe usage of strerror(errno) within ereport().

On Wed, Dec 13, 2017 at 5:57 PM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> On Wed, Dec 13, 2017 at 4:30 PM, Andres Freund <andres@anarazel.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