Re: [RFC] [RFT] [PATCH] memory zone balancing

[Andrea Arcangeli <andrea@suse.de>]

On Wed, 15 Dec 1999, Kanoj Sarcar wrote:

>-	if ((gfp_mask & __GFP_DMA) && !PageDMA(page_map))
>-		goto check_table;
>-	if (!(gfp_mask & __GFP_HIGHMEM) && PageHighMem(page_map))
>+	if (zone && (page_map->zone != zone))
> 		goto check_table;
> 	swap_attempts++;

> 		/* don't account passes over not DMA pages */
>-		if ((gfp_mask & __GFP_DMA) && !PageDMA(page))
>-			goto dispose_continue;
>-		if (!(gfp_mask & __GFP_HIGHMEM) && PageHighMem(page))
>+		if (zone && (page->zone != zone))
> 			goto dispose_continue;

> 	if (PageReserved(page)
> 	    || PageLocked(page)
>-	    || ((gfp_mask & __GFP_DMA) && !PageDMA(page))
>-	    || (!(gfp_mask & __GFP_HIGHMEM) && PageHighMem(page)))
>+	    || (zone && (page->zone != zone)))
> 		goto out_failed;


The above changes you proposed will cause you to go oom even if you still
have 16mbyte of pure (ISA-DMA) RAM free in a no-bigmem kernel. With a
bigmem kernel you'll go OOM even if you still have 1giga of memory free.

As I just told you privately in previous email the checks should be a kind
of ">" (or a more complex operation implemented in a function) and not a
"!=".

Andrea

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