Re: [PATCH] mm: slub: fix page->_count corruption (again)

[Dave Hansen]

On 01/28/2014 03:29 PM, Andrew Morton wrote:
> On Tue, 28 Jan 2014 15:17:22 -0800 Dave Hansen <dave@xxxxxxxx> 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.

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