Re: new group commit behavior not helping?

On Saturday, March 31, 2012, Jeff Janes <jeff.janes@gmail.com> wrote:
> On Saturday, March 31, 2012, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Sun, Apr 1, 2012 at 1:40 AM, Jeff Janes <jeff.janes@gmail.com> wrote:
>
>>> It looks like in your case tps was still scaling with clients when you
gave
>>> up, so clients was probably too small.
>>
>> What is kind of weird is that it actually seems to scale at almost
>> exactly half of linear.

This is expected.  A very common pattern in commits/fsync is to see
alterations between 1 and C-1,  or between 2 and C-2.

To cure that, play with commit_delay.  Don't make the mistake I did.
 Commit_delay is in micro seconds, not ms.  That didn't mater when minimum
kernel sleep was 10 or 4 ms anyway.  Now with much finer sleeps, it makes a
huge difference, so try ~5000.

Cheers

Jeff