Messages in this thread | | | Date | Fri, 14 Nov 2003 00:39:15 +0100 | From | Andrea Arcangeli <> | Subject | Re: OT: why no file copy() libc/syscall ?? |
| |
On Thu, Nov 13, 2003 at 12:22:14PM -0800, H. Peter Anvin wrote: > Followup to: <20031111085323.M8854@devserv.devel.redhat.com> > By author: Jakub Jelinek <jakub@redhat.com> > In newsgroup: linux.dev.kernel > > > > > > Actually, I think we should have a: > > > > > > long copy_fd_to_fd (int src, int dst, int len) > > > > > > type of systemcall. > > > > We have one, sendfile(2). > > > > It would be very nice if we could (a) expand the uses of sendfile(2), > and (b) have the libc do the fallback to read/write/mmap as needed.
I actually hacked cp for a while and it improved cp some point percent on normal machines.
See ftp://ftp.suse.com/pub/people/andrea/cp-sendfile/
the main downside and the reason it wasn't applied IIRC is the lack of interruption of sendfile, basically for an huge file it would take a while before C^c has any effect. The kernel isn't interrupting the syscall. This is no different from a huge read or write syscall (but read/write are never huge or the buffer would need to be huge too, not the case for sendfile that works zerocopy), so in theory we could workaround it by entering/exiting kernel multiple times just to allow the signal to be handled like in the read/write case. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |