Re: [tip:x86/mm] x86/mm: Avoid superflous leave_mm() in the TLB flush path

[Ingo Molnar <mingo@elte.hu>]

* Shaohua Li <shaohua.li@intel.com> wrote:

> On Tue, 2011-12-06 at 07:26 +0800, Linus Torvalds wrote:
> > On Mon, Dec 5, 2011 at 9:56 AM, tip-bot for Shaohua Li
> > <shaohua.li@intel.com> wrote:
> > >
> > > x86/mm: Avoid superflous leave_mm() in the TLB flush path
> > >
> > > If just one page VA tlb is required to be flushed and current
> > > task is in lazy TLB state, doing leave_mm() is superfluous
> > > because it flushes the whole TLB.  This can reduce some TLB
> > > miss.
> > 
> > Are you sure this is a good idea?
> > 
> > We may be *much* better off leaving the VM and avoiding future IPI's
> > than trying to flush pages one by one over and over again.
> > 
> > IPI's are expensive.
> > 
> > I don't think you thought this through, and if you *did* think it
> > through and actually have numbers that it's cheaper to stay with the
> > MM, I think you need to show those numbers.
>
> good point, I didn't think of it. It's unlikely we just flush 
> one tlb page. please drop the patch.

Dropped, thanks guys.

	Ingo