Re: [PATCH] vmscan: bail out of page reclaim after swap_cluster_maxpages

From: Rik van Riel
Date: Tue Nov 25 2008 - 08:33:32 EST


KOSAKI Motohiro wrote:
Sometimes the VM spends the first few priority rounds rotating back
referenced pages and submitting IO. Once we get to a lower priority,
sometimes the VM ends up freeing way too many pages.

The fix is relatively simple: in shrink_zone() we can check how many
pages we have already freed, direct reclaim tasks break out of the
scanning loop if they have already freed enough pages and have reached
a lower priority level.

However, in order to do this we do need to know how many pages we already
freed, so move nr_reclaimed into scan_control.

Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
---
Kosaki, this should address the zone scanning pressure issue.

hmmmm. I still don't like the behavior when priority==DEF_PRIORITY.
but I also should explain by code and benchmark.

Well, the behaviour when priority==DEF_PRIORITY is the
same as the kernel's behaviour without the patch...

therefore, I'll try to mesure this patch in this week.

Looking forward to it.

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