Re: [opensuse] SFTP performance degradation under Dolphin and Konqueror



On Wednesday 19 May 2010 00:24:42 Boris Epstein wrote:
On Tue, May 18, 2010 at 6:05 PM, Herbert Graeber <hgraeber@xxxxxxxxxxxx>
wrote:
Am Dienstag 18 Mai 2010, 15:59:21 schrieb Boris Epstein:
Hello everyone,

Something very curious has just been discovered here.

We have a machine running SSH/SFTP server (a Windows XP machine if
that matters). The network is a mix of 100 Mbit and 1000 Mbit ports
(12.5 and 125 MB/s, respectively). When we use command-line sftp to
transfer files we get decent speed (from 7 MB/s and upwards). When we
use graphical interfaces on either OpenSuSE or Ubuntu (and it is the
same whether it is Konqueror or Dolphin) the transfer speed drops down
to no more than 2 MB/s and sometimes even to 500 KB/s. Any idea why?

Dolpin and konqueror use kio_sftp to use the sftp protocol. kio_sftp uses
the libssh library. It's likely that it is a problem of this library,
which isn't part of KDE.

Herbert
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Thanks Herbert!

You might be on to something, however, wouldn't the command line
client (sftp) also be using that same library, libssh?

Things go fast using that client.

Herbert is right.

In KDE < 4.3 times, kio_sftp called the sftp command line binary. Since KDE
SC 4.4, it uses libssh directly, which is more robust and (theoretically)
faster. KDE already converted kio_smb from using the smbclient commandline to
using libsmbclient.

However, libssh currently only supports synchronous I/O. The sftp command
uses async I/O for better performance. libssh.org are working on implementing
async I/O too. This is the reason that KDE sftp ioslave performance is
currently worse than it has been in the past.

sftp does not use the libssh codebase. It uses the original openssh codebase,
whereas libssh is a relatively new effort to provided ssh and sftp functions
in a library.


Will
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Will Stephenson, KDE Developer, openSUSE Boosters Team
SUSE LINUX Products GmbH - Nürnberg - AG Nürnberg - HRB 16746 - GF: Markus Rex
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