On 09/26/2013 03:53 PM, Miklos Szeredi wrote:
On Thu, Sep 26, 2013 at 9:06 PM, Zach Brown <zab@xxxxxxxxxx> wrote:
But I'm not sure it's worth the effort; 99% of the use of this
interface will be copying whole files. And for that perhaps we need a
different API, one which has been discussed some time ago:
asynchronous copyfile() returns immediately with a pollable event
descriptor indicating copy progress, and some way to cancel the copy.
And that can internally rely on ->direct_splice(), with appropriate
algorithms for determine the optimal chunk size.
And perhaps we don't. Perhaps we can provide this much simpler
data-plane interface that works well enough for most everyone and can
avoid going down the async rat hole, yet again.
I think either buffering or async is needed to get good perforrmace
without too much complexity in the app (which is not good). Buffering
works quite well for regular I/O, so maybe its the way to go here as
well.
Thanks,
Miklos
Buffering misses the whole point of the copy offload - the idea is *not* to
read or write the actual data in the most interesting cases which offload the
operation to a smart target device or file system.
Regards,
Ric
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