Difference between capability and memory mapping

Yuxin Ren ryx at gwmail.gwu.edu
Wed Oct 1 17:02:20 CEST 2014

On my machine, cap mapping is faster than memory.
I do not think there is tlb flush in memory mapping. It only happens when
memory is unmapped, right?
But I found the mapping database for them are very different.
Cap mapping database is simpler than the memory's.

Thank you very much.

On Tue, Sep 30, 2014 at 5:15 PM, Adam Lackorzynski <
adam at os.inf.tu-dresden.de> wrote:

> Hi,
> On Mon Sep 29, 2014 at 13:24:56 -0400, Yuxin Ren wrote:
> > I found in the kernel, the capability mapping and memory mapping have
> very
> > similar code path.
> > But I found their performance difference is around 1000 cycles.
> > Is this true? If it is true, why do they have such large difference?
> > If this gap does not make sense, it should be a bug in my test.
> Hmm, yes, there can be a difference. Of course, the number depends on
> the hardware. Which one was slower/faster? For example, for memory there
> there could be the need to TLB flushes, so it could be slower than cap
> mappings.
> Adam
> --
> Adam                 adam at os.inf.tu-dresden.de
>   Lackorzynski         http://os.inf.tu-dresden.de/~adam/
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