Re: [PATCH] Remove OOM killer from try_to_free_pages / all_unreclaimablebraindamage

[Nick Piggin]

Marcelo Tosatti wrote:

> On Mon, Nov 08, 2004 at 02:27:31PM -0200, Marcelo Tosatti wrote:
>
> > On Fri, Nov 05, 2004 at 06:01:18PM -0200, Marcelo Tosatti wrote:
> >
> >
> > > While doing this, I noticed that kswapd will happily go to sleep 
> > > if all zones have all_unreclaimable set. I bet this is the reason 
> > > for the page allocation failures we are seeing. So the patch 
> > > also makes balance_pgdat() NOT return and go to "loop_again" 
> > > instead in case of page shortage - even if all_unreclaimable is set.
> > >
> > > Basically the "loop_again" logic IS NOT WORKING! 
> > Wrong, the loop_again logic is working, all_zones_ok will be
> > set when DEF_PRIORITY = 0. 
>
> I meant priority=DEF_PRIORITY. 

Yep

> > So the page allocation failures are happening for some other 
> > reason(s).

Pre alloc_pages / kswapd shakeup, the watermark stuff had been pretty
broken. For example, allocations would wakeup kswapd at the *same*
watermark as they would start synchronous reclaim (or fail in the case
of !wait allocations).

Why there have been apparently more reports of allocation failures
since those patches is a mystery to me. I've looked but can't find
anything to explain it. Perhaps the initial watermark calculation had
been changed slightly? I'm not sure... it could also be just be a fluke
due to chaotic effects in the mm, I suppose :|

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