Re: [PATCH] vmscan: skip freeing memory from zones with lots free

KOSAKI Motohiro
2008-11-29T10:55:15Z

> We already tried this, or something very similar in effect, I think...
>
>
> commit 26e4931632352e3c95a61edac22d12ebb72038fe
> Author: akpm <akpm>
> Date: Sun Sep 8 19:21:55 2002 +0000
>
> [PATCH] refill the inactive list more quickly
>
> Fix a problem noticed by Ed Tomlinson: under shifting workloads the
> shrink_zone() logic will refill the inactive load too slowly.
>
> Bale out of the zone scan when we've reclaimed enough pages. Fixes a
> rarely-occurring problem wherein refill_inactive_zone() ends up
> shuffling 100,000 pages and generally goes silly.
>
> This needs to be revisited - we should go on and rebalance the lower
> zones even if we reclaimed enough pages from highmem.
>
>
>
> Then it was reverted a year or two later:
>
>
> commit 265b2b8cac1774f5f30c88e0ab8d0bcf794ef7b3
> Author: akpm <akpm>
> Date: Fri Mar 12 16:23:50 2004 +0000
>
> [PATCH] vmscan: zone balancing fix
>
> We currently have a problem with the balancing of reclaim between zones: much
> more reclaim happens against highmem than against lowmem.
>
> This patch partially fixes this by changing the direct reclaim path so it
> does not bale out of the zone walk after having reclaimed sufficient pages
> from highmem: go on to reclaim from lowmem regardless of how many pages we
> reclaimed from lowmem.
>
>
> My changelog does not adequately explain the reasons.
>
> But we don't want to rediscover these reasons in early 2010 :( Some trolling
> of the linux-mm and lkml archives around those dates might help us avoid
> a mistake here.

I hope to digg past discussion archive.
Andrew, plese wait merge this patch awhile.