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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>