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Subject: Re: [patch] SLQB slab allocator (try 2)
From: Pekka Enberg <penberg@cs.helsinki.fi>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>,
       Johannes Weiner <hannes@cmpxchg.org>, Mel Gorman <mel@csn.ul.ie>,
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Date: Thu, 19 Feb 2009 15:15:34 +0200
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On Thu, 2009-02-19 at 21:51 +0900, KOSAKI Motohiro wrote:
> 2009/2/19 Pekka Enberg <penberg@cs.helsinki.fi>:
> > On Wed, 2009-02-18 at 09:48 +0900, KOSAKI Motohiro wrote:
> >> > > In addition, if pekka patch (SLAB_LIMIT = 8K) run on ia64, 16K allocation
> >> > > always fallback to page allocator and using 64K (4 times memory consumption!).
> >> >
> >> > Yes, correct, but SLUB does that already by passing all allocations over
> >> > 4K to the page allocator.
> >>
> >> hmhm
> >> OK. my mail was pointless.
> >>
> >> but why? In my understanding, slab framework mainly exist for efficient
> >> sub-page allocation.
> >> the fallbacking of 4K allocation in 64K page-sized architecture seems
> >> inefficient.
> >
> > I don't think any of the slab allocators are known for memory
> > efficiency. That said, the original patch description sums up the
> > rationale for page allocator pass-through:
> >
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=aadb4bc4a1f9108c1d0fbd121827c936c2ed4217
> >
> > Interesting enough, there seems to be some performance gain from it as
> > well as seen by Mel Gorman's recent slab allocator benchmarks.
> 
> Honestly, I'm bit confusing.
> above url's patch use PAGE_SIZE, but not 4K nor architecture independent value.
> Your 4K mean PAGE_SIZE?

Yes, I mean PAGE_SIZE. 4K page sizes are hard-wired into my brain,
sorry :-)