linux-kernel - Re: [RFC][PATCH 0/2] Quicklist is slighly problematic.

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Message-ID: <20080821131404.GC26567@sgi.com>
Date:	Thu, 21 Aug 2008 08:14:04 -0500
From:	Robin Holt <holt@....com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Robin Holt <holt@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	tokunaga.keiich@...fujitsu.com, stable@...nel.org
Subject: Re: [RFC][PATCH 0/2] Quicklist is slighly problematic.

On Thu, Aug 21, 2008 at 08:07:43AM -0500, Christoph Lameter wrote:
> Robin Holt wrote:
> >
> > Index: ia64-cleanups/include/linux/quicklist.h
> > ===================================================================
> > --- ia64-cleanups.orig/include/linux/quicklist.h	2008-08-20 21:35:10.000000000 -0500
> > +++ ia64-cleanups/include/linux/quicklist.h	2008-08-20 21:38:00.891943270 -0500
> > @@ -66,6 +66,15 @@ static inline void __quicklist_free(int 
> >  
> >  static inline void quicklist_free(int nr, void (*dtor)(void *), void *pp)
> >  {
> > +#ifdef CONFIG_NUMA
> > +	unsigned long nid = page_to_nid(virt_to_page(pp));
> > +
> > +	if (unlikely(nid != numa_node_id())) {
> > +		free_page((unsigned long)pp);
> > +		return;
> > +	}
> > +#endif
> > +
> >  	__quicklist_free(nr, dtor, pp, virt_to_page(pp));
> >  }
> >  
> 
> We removed this code because it frees a page before the TLB flush has been
> performed. This code segment was the reason that quicklists were not accepted
> for x86.

How could we do this.  It was a _HUGE_ problem on altix boxes.  When you
started a jobs with a large number of MPI ranks, they would all start
from the shepherd process on a single node and the children would
migrate to a different cpu.  Unless subsequent jobs used enough memory
to flush those remote quicklists, we would end up with a depleted node
that never reclaimed.

Thanks,
Robin
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