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

[Rik van Riel]

Andrew Morton wrote:
> On Sat, 29 Nov 2008 13:41:34 -0500 Rik van Riel <riel@xxxxxxxxxx> wrote:
>
> > Andrew Morton wrote:
> > > On Sat, 29 Nov 2008 12:58:32 -0500 Rik van Riel <riel@xxxxxxxxxx> wrote:
> > >
> > > > > Will this new patch reintroduce the problem which
> > > > > 26e4931632352e3c95a61edac22d12ebb72038fe fixed?
> > No, that problem is already taken care of by the fact that
> > active pages always get deactivated in the current VM,
> > regardless of whether or not they were referenced.
>
> err, sorry, that was the wrong commit. 
> 26e4931632352e3c95a61edac22d12ebb72038fe _introduced_ the problem, as
> predicted in the changelog.
>
> 265b2b8cac1774f5f30c88e0ab8d0bcf794ef7b3 later fixed it up.

The patch I sent in this thread does not do any baling out,
it only skips zones where the number of free pages is more
than 4 times zone->pages_high.

Equal pressure is still applied to the other zones.

This should not be a problem since we do not enter direct
reclaim unless the free pages in every zone in our zonelist
are below zone->pages_low.

Zone skipping is only done by tasks that have been in the
direct reclaim code for a long time.

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