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Date: Tue, 28 Jan 2014 15:52:47 -0800 From: Dave Hansen <dave@...1.net> To: Andrew Morton <akpm@...ux-foundation.org> CC: linux-mm@...ck.org, linux-kernel@...r.kernel.org, cl@...ux-foundation.org, penberg@...nel.org, mpm@...enic.com, pshelar@...ira.com, Wu Fengguang <fengguang.wu@...el.com> Subject: Re: [PATCH] mm: slub: fix page->_count corruption (again) On 01/28/2014 03:29 PM, Andrew Morton wrote: > On Tue, 28 Jan 2014 15:17:22 -0800 Dave Hansen <dave@...1.net> wrote: > This code is borderline insane. No argument here. > Yes, struct page is special and it's worth spending time and doing > weird things to optimise it. But sheesh. > > An alternative is to make that cmpxchg quietly go away. Is it more > trouble than it is worth? It has measurable performance benefits, and the benefits go up as the cost of en/disabling interrupts goes up (like if it takes you a hypercall). Fengguang, could you run a set of tests for the top patch in this branch to see if we'd be giving much up by axing the code? https://github.com/hansendc/linux/tree/slub-nocmpxchg-for-Fengguang-20140128 I was talking with one of the distros about turning it off as well. They mentioned that they saw a few performance regressions when it was turned off. I'll share details when I get them. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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