Horton
Menu

Re: increasing the default WAL segment size

Simon Riggs <simon@2ndquadrant.com>

View thread
From: Simon Riggs <simon@2ndquadrant.com>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Beena Emerson <memissemerson@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Stephen Frost <sfrost@snowman.net>, David Steele <david@pgmasters.net>, tushar <tushar.ahuja@enterprisedb.com>, Prabhat Sahu <prabhat.sahu@enterprisedb.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>
Date: 2017-04-05T19:42:10Z
Lists: pgsql-hackers 
On 5 April 2017 at 08:36, Peter Eisentraut
<peter.eisentraut@2ndquadrant.com> wrote:
> On 4/5/17 06:04, Beena Emerson wrote:
>>     I suggest the next step is to dial up the allowed segment size in
>>     configure and run some tests about what a reasonable maximum value could
>>     be.  I did a little bit of that, but somewhere around 256 MB, things got
>>     really slow.
>>
>>
>> Would it be better if just increase the limit to 128MB for now?
>> In next we can change the WAL file name format and expand the range?
>
> I don't think me saying it felt a bit slow around 256 MB is a proper
> technical analysis that should lead to the conclusion that that upper
> limit should be 128 MB. ;-)
>
> This tells me that there is a lot of explore and test here before we
> should let it loose on users.

Agreed

> I think the best we should do now is spend a bit of time exploring
> whether/how larger values of segment size behave, and bump the hardcoded
> configure limit if we get positive results.  Everything else should
> probably be postponed.
>
> (Roughly speaking, to get started, this would mean compiling with
> --with-wal-segsize 16, 32, 64, 128, 256, run make check-world both
> sequentially and in parallel, and take note of a) passing, b) run time,
> c) disk space.)

I've committed the rest of Beena's patch to allow this testing to
occur up to 1024MB.

-- 
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

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

  1. Make WAL segment size configurable at initdb time.

  2. Perform only one ReadControlFile() during startup.

  3. Introduce BYTES unit for GUCs.

  4. Remove useless duplicate inclusions of system header files.

  5. Refactor other replication commands to use DestRemoteSimple.

  6. Add a SHOW command to the replication command language.

  7. Add a new DestReceiver for printing tuples without catalog access.

  8. Support fls().

  9. Extend yesterday's patch making BLCKSZ and RELSEG_SIZE configurable to also

  10. Commit the reasonably uncontroversial parts of J.R. Nield's PITR patch, to

  11. XLOG (also known as WAL -:)) Bootstrap/Startup/Shutdown.

  12. Transaction log manager core code.