Re: Performance features the 4th

Matthew T. O'Connor wrote:

> ----- Original Message -----
> From: "Jan Wieck" <JanWieck(at)Yahoo(dot)com>
>> Tom Lane wrote:
>> > Gaetano and a couple of other people did experiments that seemed to show
>> > it was useful. I think we'd want to change the shape of the knob per
>> > later suggestions (sleep 10 ms every N blocks, instead of N ms every
>> > block) but it did seem that there was useful bang for little buck there.
>>
>> I thought it was "sleep N ms every M blocks".
>>
>> Have we seen any numbers? Anything at all? Something that gives us a
>> clue by what factor one has to multiply the total time a "VACUUM
>> ANALYZE" takes, to get what effect in return?
>
> I have some time on sunday to do some testing. Is there a patch that I can
> apply that implements either of the two options? (sleep 10ms every M blocks
> or sleep N ms every M blocks).
>
> I know Tom posted the original patch that sleept N ms every 1 block (where N
> is > 10 due to OS limitations). Jan can you post a patch that has just the
> sleep code in it? Or should it be easy enough for me to cull out of the
> larger patch you posted?

Sorry for the delay, had to finish some other concept yesterday (will be
published soon).

The attached patch adds

vacuum_group_delay_size = 10 (range 1-1000)
vacuum_group_delay_msec = 0 (range 0-1000)

and does the sleeping via select(2). It does it only at the same places
where Tom had done the usleep() in his hack, so I guess there is still
some more to do besides the documentation, before it can be added to
7.4.1. But it should be enough to get some testing done.

Jan

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