On Thu, Sep 26, 2013 at 08:06:41PM +0200, Miklos Szeredi wrote: > On Thu, Sep 26, 2013 at 5:34 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Thu, Sep 26, 2013 at 10:58:05AM +0200, Miklos Szeredi wrote: > >> On Wed, Sep 25, 2013 at 11:07 PM, Zach Brown <zab@xxxxxxxxxx> wrote: > >> >> A client-side copy will be slower, but I guess it does have the > >> >> advantage that the application can track progress to some degree, and > >> >> abort it fairly quickly without leaving the file in a totally undefined > >> >> state--and both might be useful if the copy's not a simple constant-time > >> >> operation. > >> > > >> > I suppose, but can't the app achieve a nice middle ground by copying the > >> > file in smaller syscalls? Avoid bulk data motion back to the client, > >> > but still get notification every, I dunno, few hundred meg? > >> > >> Yes. And if "cp" could just be switched from a read+write syscall > >> pair to a single splice syscall using the same buffer size. > > > > Will the various magic fs-specific copy operations become inefficient > > when the range copied is too small? > > We could treat spice-copy operations just like write operations (can > be buffered, coalesced, synced). > > 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. - z -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
