Re: [RFC] extending splice for copy offloading

Eric Wong
2013-09-11T21:17:25Z

Zach Brown <zab@redhat.com> wrote:
> Towards the end of that thread Eric Wong asked why we didn't just
> extend splice. I immediately replied with some dumb dismissive
> answer. Once I sat down and looked at it, though, it does make a
> lot of sense. So good job, Eric. +10 Dummie points for me.

Thanks for revisiting that :>

> Some things to talk about:
> - I really don't care about the naming here. If you do, holler.

Exposing "DIRECT" to userspace now might confuse users into expecting
O_DIRECT behavior. I say this as an easily-confused user.

In the future, perhaps O_DIRECT behavior can become per-splice (instead
of just per-open) and can save SPLICE_F_DIRECT for that.

> - We might want different flags for file-to-file splicing and acceleration
> - We might want flags to require or forbid acceleration

> - We might want to provide all these flags to sendfile, too

Another syscall? I prefer not. Better to just maintain the sendfile
API as-is for compatibility reasons and nudge users towards splice.

> Thoughts? Objections?

I'll try to test/comment more in a week or two (not much time for
computing until then).