On Mon, 16 Apr 2007, Hugh Dickins wrote:
> > > Compromise patch below: would that be satisfactory to you, David?
> >
> > I really like the patch, but for perhaps a slightly different reason:
> > we're only flushing ranges that have been shown to need it. We aren't
> > completely flushing the entire mm which is likely to be excessive in
> > situations where we're actually using /proc/pid/clear_refs in combination
> > with /proc/pid/smaps for memory footprint approximation (i.e. it's on a
> > fine granularity).
>
> It would be more of a reason to like the patch, if more architectures
> actually implemented flush_tlb_range as anything different from
> flush_tlb_mm ;) Sadly, few can do better than flush_tlb_mm: ia64
> is the exception I remember, and maybe a couple of others. I put
> flush_tlb_range there merely because it seems more appropriate,
> but it's rather deceptive.
>
Sure, but what I really like about the patch is that we're only flushing
something if !flush_end in the first place. So we can eliminate any TLB
flushing if that VMA didn't need it; that's a change from the current
behavior. And since the most obvious use-case for /proc/pid/clear_refs is
in conjunction with /proc/pid/smaps for approximating memory footprint,
we'll end up saving TLB flushes because the granularity with which that
measurement is taken is usually very fine.
Acked-by: David Rientjes <[email protected]>
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