On 18 Nov 2021, at 08:36, Gernot Heiser
<[email protected]<mailto:[email protected]>> wrote:
On 18 Nov 2021, at 08:24, Gerwin Klein
<[email protected]<mailto:[email protected]>> wrote:
The page reports the 0-length numbers. The idea is that IPC should fit into
registers, the 10 case is the one that make it spill into memory deliberately.
That number is good to know for development, but should not be the main
performance characteristic.
Note that whether data is transferred solely in registers or using a memory
buffer does not make a big difference on contemporary hardware. However, our
present implementation reverts to the slow path as soon as the message size
overflows the physical message registers, which will make the PIC much slower.
Yes I should have mentioned that. If you look at the raw numbers for x86, eg.
at https://github.com/seL4/sel4bench/actions/runs/1469475721#artifacts, fast
path/no fast path is almost equal for length 10. You get a tiny bit better
performance for length 10 when the fast path is switched off completely,
because it doesn't first have to test whether to take the fast path or not.
Cheers,
Gerwin
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