[knem-devel] The unexpected performance of DMA memcopy with knem

Zheng Da zhengda1936 at gmail.com
Tue Jul 30 13:35:19 CEST 2013


Thank you, Brice.

On Mon, Jul 29, 2013 at 11:11 AM, Brice Goglin <Brice.Goglin at inria.fr>wrote:
>
>
> > The way to fix this is to stop using the netdma channels and directly
> > acquire physical channels from KNEM.
>
> KNEM actually currently uses the "general purpose" channels, those are
> improperly distributed per cpu as explained above. One ugly way to solve
> the issue would be to manually migrate to another CPUs so that we get a
> channel with correct locality from the "general purpose" allocator. But
> that's ugly.
>
> There's another low-level acquire interface but it doesn't work for the
> channels we are considering here. So I don't think there's any clean
> solution for now. I'll ask the kernel guys and report the locality
> issue. We'll see what they say.

Could you keep me informed of the progress? I'm very interested in how the
kernel guys will fix the problem.

Thanks,
Da
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