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SubjectRe: Syslets, Threadlets, generic AIO support, v6
Linus Torvalds a écrit :
>
> On Wed, 30 May 2007, Eric Dumazet wrote:
>> So yes, reimplement sendfile() should help to find last splice() bugs, and as
>> a bonus it could add non blocking disk io, (O_NONBLOCK on input file ->
>> socket)
>
> Well, to get those kinds of advantages, you'd have to use splice directly,
> since sendfile() hasn't supported nonblocking disk IO, and the interface
> doesn't really allow for it.

sendfile() interface doesnt allow it, but if you open("somediskfile", O_RDONLY
| O_NONBLOCK), then splice() based sendfile() can perform a non blocking disk
io, (while starting an io with readahead)

I actually use this trick myself :)

(splice(disk -> pipe, NONBLOCK), splice(pipe -> worker))

non blocking disk io, + zero copy :)

>
> In fact, since nonblocking accesses require also some *polling* method,
> and we don't have that for files, I suspect the best option for those
> things is to simply mix AIO and splice(). AIO tends to be the right thing
> for disk waits (read: short, often cached), and if we can improve AIO
> performance for the cached accesses (which is exactly what the threadlets
> should hopefully allow us to do), I would seriously suggest going that
> route.
>
> But the pure "use splice to _implement_ sendfile()" thing is worth doing
> for all the other reasons, even if nonblocking file access is not likely
> one of them.
>
> Linus
>
>

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