Re: Major performance regressions in 3.7rc1/2

From: Hugh Dickins
Date: Tue Oct 23 2012 - 00:20:56 EST

On Mon, 22 Oct 2012, Andrew Morton wrote:
> On Mon, 22 Oct 2012 21:45:02 +0200
> Julian Wollrath <julian.wollrath@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hello,
> >
> > seems like I found the other bad commit. Everything, which means
> > v3.7-rc*, works fine again with commit e6c509f85 (mm: use
> > clear_page_mlock() in page_remove_rmap()) and commit 957f822a0 (mm,
> > numa: reclaim from all nodes within reclaim distance) revoked.
> Thanks. Let's add some cc's. Can you please describe your workload
> and some estimate of the slowdown?

I'm currently assuming that my clear_page_mlock() commit is innocent
of this: it went in just two before David's numa reclaim commit, and
I don't see how mine could have any such marked effect: I'm thinking
it was just a bisection hiccup that implicated it.

Julian (or Patrik), what do you find if you revert the numa reclaim
commit but leave in the clear_page_mlock commit? Or vice versa.

Whereas David's numa reclaim distance commit does look suspicious to
me: as I read it (perhaps wrongly), zone_reclaim_mode would previously
have stayed 0 if all nodes were close or equidistant (e.g. CONFIG_NUMA=y
on a non-NUMA machine), but now it would be 1 in this case, invoking
zone_reclaim() more frequently than before.


> Patrik has also seen this and his description is
> : I'm using an Asus Zenbook UX31E and have been installing all RCs in
> : hope of improving the Wireless and Touchpad functionality.
> : However, when trying 3.7 (rc1 and now rc2) I have major performance issues.
> :
> : Easiest way to reproduce is to launch and play a game like Nexuiz,
> : where the computer will lag, stutter and freeze until the machine is
> : unresponsive within a couple of minutes.
> : But an easy workload like browsing will also cause lags when switching
> : tabs or redrawing a web page after a tab switch.
> : Basically 3.7 is unusable for this machine.
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