Re: kswapd @ 60-80% CPU during heavy HD i/o.

[Rik van Riel <riel@conectiva.com.br>]

On Mon, 1 May 2000, David S. Miller wrote:
> From: Rik van Riel <riel@conectiva.com.br>
>    On Mon, 1 May 2000, David S. Miller wrote:
> 
>    > BTW, what loop are you trying to "continue;" out of here?
>    > 
>    > +			    do {
>    >  				if (tsk->need_resched)
>    >  					schedule();
>    >  				if ((!zone->size) || (!zone->zone_wake_kswapd))
>    >  					continue;
>    >  				do_try_to_free_pages(GFP_KSWAPD, zone);
>    > +			   } while (zone->free_pages < zone->pages_low &&
>    > +					   --count);
>    > 
>    > :-)  Just add a "next_zone:" label at the end of that code and
>    > change the continue; to a goto next_zone;
> 
>    I want kswapd to continue with freeing pages from this zone if
>    there aren't enough free pages in this zone. This is needed
>    because kswapd used to stop freeing pages even if we were below
>    pages_min...
> 
> Rik, zone_wake_kswapd implies this information, via what
> __free_pages_ok does to that flag.

Indeed, I should have moved the test for zone->zone_wake_kswapd to 
before the loop. But using zone->zone_wake_kswapd for the test isn't
really enough since that is only turned off if zone->free_pages 
reaches zone->pages_high, but we probably don't want to do agressive
swapout when we're already above zone->pages_low ...

(just background swapping that happens incidentally when we're
swapping stuff for other zones)

regards,

Rik
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