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SubjectRe: TLB evaluation for Linux

On Tue Sep 02 09:43:53 EDT 2008, Arjan van de Ven
<arjan@infradead.org> wrote:

> On Tue, 2 Sep 2008 00:12:03 -0400 (EDT)
> "CHADHA,VINEET" <vineet@ufl.edu> wrote:
>

> note that linux only does an ipi to processors that actually are
> currently running a thread of the same program (or a kernel
> thread).
> Old versions didn't do this (they also IPI'd idle processors),
> but
> on modern cpus and modern kernels that's not supposed to happen
> anymore
> (the C-states that flush the tlb anyway now do the kernel side
> bookkeeping as well to avoid the wakeup+useless flush)

Interesting to know about it.

> one of the problems is that invlpg is rather expensive; in
> long-ago
> experiments the threshold was like around a handful of pages
> already.
> At that point.. all the bookkeeping isn't likely to be a win.
> Esp since a tlb refill on x86 is quite cheap.

Yeah that is possible. Do you have link to any published work ? It
would be still interesting to characterize and compare behavior
for new workloads scenarios such as virtual machines.



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