Re: [PATCH] 1/5 VM changes: zone-pressure.patch

From: Nikita Danilov (Nikita@Namesys.COM)
Date: Thu Jul 17 2003 - 08:50:44 EST


Andrew Morton writes:
> Nikita Danilov <Nikita@Namesys.COM> wrote:
> >
> > > OK, fixes a bug.
> >
> > What bug?
>
> Failing to consider mapped pages on the active list until the scanning
> priority gets large.
>
> I ran up your five patches on a 256MB box, running `qsbench -m 350'. It got
> all slow then the machine seized up. I'll poke at it some.
>

My understanding of this is following:

1. kswapd/balance_pgdat runs through all priorities, but fails to rise
zone->free_pages above zone->pages_min. So it exet. Which is strange.

2. nobody is going to wake it up, because all memory allocators are
looping indefinitely in that newly introduced do_retry loop inside
__alloc_pages.

I think either wakeup_kswapd() should be called in __alloc_pages()
before goto rebalance, or kswapd should loop until it restores all zones
to the balance (actually, comment before balance_pgdat() says it does),
or both.

Nikita.
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