Re: [PATCH] mm, page_alloc: fix the duplicate save/ressave irq

[Mel Gorman <mgorman@techsingularity.net>]

On Tue, Mar 14, 2017 at 08:06:34PM +0800, zhong jiang wrote:
> >> you mean the removing cpu maybe  handle the IRQ, it will result in the incorrect pcpu->count ?
> >>
> > Yes, if it hasn't had interrupts disabled yet at the time of the drain.
> > I didn't check, it probably is called from a context that disables
> > interrupts but the fact you're not sure makes me automatically wary of
> > the patch particularly given how little difference it makes for the common
> > case where direct reclaim failed triggering a drain.
> >
> >> but I don't sure that dying cpu remain handle the IRQ.
> >>
> > You'd need to be certain to justify the patch.
> >
>  Hi,  Mel
>    
>     by code review,  I see the cpu hotplug will only register the notfier to callback the function without
>   interrupt come.  is it right ??
> 

That sentence is impossible to parse meaningfully. The patch was
posted without verifying it made any performance difference (it almost
certainly won't) and without checking all the callers are actually safe
(which you're still not sure of).

Consider the patch NAK'd on both grounds (marginal, if any improvement
with no checking that the patch is safe).

-- 
Mel Gorman
SUSE Labs

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