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

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Date:	Sat, 24 Jan 2009 11:11:48 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka J Enberg <penberg@...helsinki.fi>,
	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 Sat, 2009-01-24 at 02:37 +1100, Nick Piggin wrote:
> 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.
Client/server model and distributed systems are popular. To be flexible,
these applications mostly can be configured in one machine, or in a group of
machines. If in one machine, they are used to communicate with network loopback.
I once touched a big distributed telecom application which use UDP to communicate
between front-end and back-end. If they merge front-end and back-end to one machine
based on some customers' requirements to reduce cost, that will be an example.

> 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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