linux-kernel - Re: kswapd min order, slub max order [was Re: -mm merge plans for 2.6.24]

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Message-Id: <200710021910.58983.nickpiggin@yahoo.com.au>
Date:	Tue, 2 Oct 2007 19:10:58 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Chritoph Lameter <clameter@....com>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: kswapd min order, slub max order [was Re: -mm merge plans for 2.6.24]

On Wednesday 03 October 2007 02:06, Hugh Dickins wrote:
> On Mon, 1 Oct 2007, Andrew Morton wrote:
> > #
> > # slub && antifrag
> > #
> > have-kswapd-keep-a-minimum-order-free-other-than-order-0.patch
> > only-check-absolute-watermarks-for-alloc_high-and-alloc_harder-allocation
> >s.patch slub-exploit-page-mobility-to-increase-allocation-order.patch
> > slub-reduce-antifrag-max-order.patch
> >
> >   I think this stuff is in the "mm stuff we don't want to merge"
> > category. If so, I really should have dropped it ages ago.
>
> I agree.  I spent a while last week bisecting down to see why my heavily
> swapping loads take 30%-60% longer with -mm than mainline, and it was
> here that they went bad.  Trying to keep higher orders free is costly.

Yeah, no there's no way we'd merge that.


> On the other hand, hasn't SLUB efficiency been built on the expectation
> that higher orders can be used?  And it would be a twisted shame for
> high performance to be held back by some idiot's swapping load.

IMO it's a bad idea to create all these dependencies like this.

If SLUB can get _more_ performance out of using higher order allocations,
then fine. If it is starting off at a disadvantage at the same order, then it
that should be fixed first, right?

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