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. Thanks, Miklos -- 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
