Re: [patch] balanced highmem subsystem under pre7-9

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

On Fri, 12 May 2000, Ingo Molnar wrote:

> --- linux/mm/vmscan.c.orig	Fri May 12 12:28:58 2000
> +++ linux/mm/vmscan.c	Fri May 12 12:29:50 2000
> @@ -543,13 +543,14 @@
>  				something_to_do = 1;
>  				do_try_to_free_pages(GFP_KSWAPD);
>  				if (tsk->need_resched)
> -					schedule();
> +					goto sleep;
>  			}
>  			run_task_queue(&tq_disk);
>  			pgdat = pgdat->node_next;
>  		} while (pgdat);
>  
>  		if (!something_to_do) {
> +sleep:
>  			tsk->state = TASK_INTERRUPTIBLE;
>  			interruptible_sleep_on(&kswapd_wait);
>  		}

This is wrong. It will make it much much easier for processes to
get killed (as demonstrated by quintela's VM test suite).

The correct fix probably is to have the _same_ watermark for
something_to_do *and* the "easy allocation" in __alloc_pages.

(very much untested patch versus pre7-9 below)

regards,

Rik
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--- vmscan.c.orig	Thu May 11 12:13:08 2000
+++ vmscan.c	Fri May 12 19:46:49 2000
@@ -542,8 +542,9 @@
 				zone_t *zone = pgdat->node_zones+ i;
 				if (!zone->size || !zone->zone_wake_kswapd)
 					continue;
-				something_to_do = 1;
 				do_try_to_free_pages(GFP_KSWAPD);
+				if (zone->free_pages < zone->pages_low)
+					something_to_do = 1;
 				if (tsk->need_resched)
 					schedule();
 			}

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