Re: [PATCH] kswapd shall not sleep during page shortage

[Andrew Morton <akpm@osdl.org>]

Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
>
> 
> Andrew,
> 
> I was wrong last time I read balance_pgdat() when I thought kswapd
> couldnt sleep under page shortage. 
> 
> It can, because all_zones_ok is set to "1" inside the 
> "priority=DEF_PRIORITY; priority >= 0; priority--" loop.
> 
> So this patch sets "all_zones_ok" to zero even if all_unreclaimable 
> is set, avoiding it from sleeping when zones are under page short.
> 

Does this solve any observed problem?  What testing was done, and what were
the results??

> 
> --- linux-2.6.10-rc1-mm2/mm/vmscan.c.orig	2004-11-09 16:38:04.480873424 -0200
> +++ linux-2.6.10-rc1-mm2/mm/vmscan.c	2004-11-09 16:38:08.624243536 -0200
> @@ -1033,15 +1033,17 @@
>  				if (zone->present_pages == 0)
>  					continue;
>  
> -				if (zone->all_unreclaimable &&
> -						priority != DEF_PRIORITY)
> -					continue;
> -
>  				if (!zone_watermark_ok(zone, order,
>  						zone->pages_high, 0, 0, 0)) {
>  					end_zone = i;
> -					goto scan;
> +					all_zones_ok = 0;
>  				}
> +
> +				if (zone->all_unreclaimable &&
> +						priority != DEF_PRIORITY)
> +					continue;
> +
> +				goto scan;
>  			}
>  			goto out;
>  		} else {
--
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