linux-kernel - Re: [PATCH] SLUB: revert direct page allocator pass through

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Message-Id: <200901240237.10522.nickpiggin@yahoo.com.au>
Date:	Sat, 24 Jan 2009 02:37:09 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Pekka J Enberg <penberg@...helsinki.fi>,
	yanmin_zhang@...ux.intel.com, Andi Kleen <andi@...stfloor.org>,
	Matthew Wilcox <matthew@....cx>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] SLUB: revert direct page allocator pass through

On Saturday 24 January 2009 02:27:29 Christoph Lameter wrote:
> On Sat, 24 Jan 2009, Nick Piggin wrote:
> > > I thought higher order allocations were not supposed to be used in
> > > performance critical paths?
> >
> > ? You use them all the time in SLUB alone.
>
> But SLUB compensates for the slow higher order allocs by using them as
> buffers for smaller objects.. The higher order allocs are in the slow
> paths.

I don't quite know what you're asking of me. If you see higher order
allocations in performance critical code, then you answer your own
question?

However, I don't know if netperf udp 4K over loopback is totally
realistic. Maybe real network drivers have different allocation patterns.
If I were you I wouldn't be too hasty to make big changes based on that
alone, if it could introduce regression in somewhere more important.

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