Re: kswapd min order, slub max order [was Re: -mm merge plans for 2.6.24]
From: Nick Piggin
Date: Tue Oct 02 2007 - 21:42:51 EST
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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