Re: [PATCH V3]hrtimer: Fix a performance regression by disablereprogramming in remove_hrtimer

[Mike Galbraith]

On Thu, 2013-08-08 at 17:04 +0800, ethan.zhao wrote:

> So, it's Peter's patch workingâââ

Yes.  My patch killed the nohz tick start/stop overhead prior to 3.8,
but in 3.8, the menu governor changes added more high frequency timer
banging that negated its effect.  In 3.9, mwait went away, making core2
boxen very sad, and in 3.10 all of x86 got generic idle, making my boxen
even sadder.

select_idle_sibling() (the thing that makes us schedule pipe-test and
many other things cross core if there's an idle core available) has
always been two-faced, doing both good and evil.. but with recent work,
it's leaning more toward evil than ever before.

-Mike

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