Horton

Re: Spread checkpoint sync

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: pgsql-hackers@postgresql.org
Date: 2011-01-15T21:28:17Z
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. Add new buffers_backend_fsync field to pg_stat_bgwriter.

On Sat, Jan 15, 2011 at 10:31 AM, Greg Smith <greg@2ndquadrant.com> wrote:
> That's going to give worse performance than the current code in some cases.

OK.

>> How does the checkpoint target give you any time to sync them?  Unless
>> you squeeze the writes together more tightly, but that seems sketchy.
>
> Obviously the checkpoint target idea needs to be shuffled around some too.
>  I was thinking of making the new default 0.8, and having it split the time
> in half for write and sync.  That will make the write phase close to the
> speed people are seeing now, at the default of 0.5, while giving some window
> for spread sync too.  The exact way to redistribute that around I'm not so
> concerned about yet.  When I get to where that's the most uncertain thing
> left I'll benchmark the TPS vs. latency trade-off and see what happens.  If
> the rest of the code is good enough but this just needs to be tweaked,
> that's a perfect thing to get beta feedback to finalize.

That seems like a bad idea - don't we routinely recommend that people
crank this up to 0.9?  You'd be effectively bounding the upper range
of this setting to a value to the less than the lowest value we
recommend anyone use today.

-- 
Robert Haas
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