On Tue, Mar 26, 2013 at 05:23:03PM +0100, Stefan Hajnoczi wrote: > On Tue, Mar 26, 2013 at 02:21:39PM +0000, Richard W.M. Jones wrote: > > On Tue, Mar 26, 2013 at 10:38:46AM +0000, Richard W.M. Jones wrote: > > > + /* According to the docs, this just updates a field in the > > > + * sftp_handle structure, so there is no network traffic and it > > > + * cannot fail. > > > + */ > > > + libssh2_sftp_seek64(s->sftp_handle, offset); > > > > While I was looking at the performance of qemu+ssh vs sshfs, I noticed > > that the line above has a catastrophic effect on performance, since it > > causes all readahead data to be thrown away. Ooops. I'm reworking > > the patch to make seeking more intelligent. > > Should libssh2 be smarter and preserve the readahead when offsets are > contiguous? > > It makes sense to fix in QEMU for older libssh2 binaries, but the real > fix might be for libssh2 to be smart.
It's quite tricky to fix at the libssh2 API level ... However I sent a preliminary patch upstream: http://www.libssh2.org/mail/libssh2-devel-archive-2013-03/0019.shtml Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top
