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SubjectRe: Memory Problem in 2.4.9 ?
Date
On August 22, 2001 09:05 pm, Marcelo Tosatti wrote:
> On Wed, 22 Aug 2001, Daniel Phillips wrote:
> > What can we do right now? We could always just comment out the alloc failed
> > message. The result will be a lot of busy waiting on dirty page writeout
> > which will work but it will keep us from focussing on the question: how did
> > we get so short of bounce buffers? Well, maybe we are submitting too much IO
> > without intelligent throttling (/me waves at Ben). That sounds like the
> > place to attack first.
>
> We can just wait on the writeout of lowmem buffers at page_launder()
> (which will not cause IO buffering since we are doing lowmem IO, duh), and
> then we are done.
>
> Take a look at the patch I posted before (__GFP_NOBOUNCE).

A little light reading for a Wednesday afternoon ;-)

Nice hack, way to go. So this will wait synchronously in try_to_free_buffers
if we have to go around twice in alloc_bounce_page or alloc_bounce_bh (the
latter eventually resulting in a page_alloc from kmem_cache grow).

What does SLAB_LEVEL_MASK do? Did you find out by hitting the BUG when you
tried the patch? Anyway, it needs a comment.

I had in mind a completely different approach to try, using a semaphore to
count bounce buffers, and block when they run out. Your patch fits the
pattern of the current busy-waiting strategy much better. It's the right
thing to do.

OK, race you to the next bug ;-)

--
Daniel

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