
> Or...  It seems to me that we have been observing something on the order 
> of 10x-20x slowdown for vacuuming a table.  I think this is WAY 
> overcompensating for the original problems, and would cause it's own 
> problem as mentioned above.   Since the granularity of delay seems to be 
> the problem can we do more work between delays? Instead of sleeping 
> after every page (I assume this is what it's doing) perhaps we should 
> sleep every 10 pages,

I also think doing more than one page per sleep is advantageous since
it would still allow the OS to do it's readahead optimizations.
I suspect those would fall flat if only one page is fetched per sleep.

Andreas

Tue, 4 Nov 2003 14:47:37 +0100
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>
Re: Experimental patch for inter-page delay in VACUUM
Zeugswetter Andreas SB SD wrote:

>>Or...  It seems to me that we have been observing something on the order 
>>of 10x-20x slowdown for vacuuming a table.  I think this is WAY 
>>overcompensating for the original problems, and would cause it's own 
>>problem as mentioned above.   Since the granularity of delay seems to be 
>>the problem can we do more work between delays? Instead of sleeping 
>>after every page (I assume this is what it's doing) perhaps we should 
>>sleep every 10 pages,
>>    
>>
>
>I also think doing more than one page per sleep is advantageous since
>it would still allow the OS to do it's readahead optimizations.
>I suspect those would fall flat if only one page is fetched per sleep.
>  
>

So maybe the setting shouldn't be "n ms wait between vacuum actions" but 
"vacuum pages to handle before sleeping 10 ms".

Regards,
Andreas



Tue, 04 Nov 2003 14:55:34 +0100
Andreas Pflug <pgadmin@pse-consulting.de>
Re: Experimental patch for inter-page delay in VACUUM