[Samba] Performance with XP64

Glenn Maynard glenn at zewt.org
Tue Mar 15 14:35:32 MDT 2011

On Tue, Mar 15, 2011 at 3:36 PM, Volker Lendecke
<Volker.Lendecke at sernet.de>wrote:

> On Tue, Mar 15, 2011 at 02:28:37PM -0400, Glenn Maynard wrote:
> > tcpdump reading a 256MB file (from tmpfs) on XP64:
> > http://zewt.org/~glenn/samba.tcpdump.gz, 56M/sec
> That's pretty much what you would expect. The trace shows
> that your program reads sequentially in 61k chunks. Given

My program reads in 1M chunks; it's the OS splitting apart the reads.

that your network latency is roughly 600 microseconds,
> ftp://pserver.samba.org/pub/unpacked/junkcode/expected_throughput.pl
gives 55MB/sec. You might want to try smbclient, that does
> larger parallel reads, or a copy program that uses multiple
> threads simultaneously.

That's what I'd expect if things are as broken as they look from that dump:
the client (XP) isn't buffering requests at all, so the window caps out at
64k.  The mail from earlier[1] suggests that some people get much better
speed from other servers (though without enough information to really be
useful).  I don't know the protocol, so I can't tell if there's something
preventing the client from buffering multiple read requests, for example,
which I'd expect of any network FS.

Multiple threads isn't a good solution (at these speeds, it's liable to
severely hurt streaming performance), and in any case it doesn't help actual
use, with real applications.

[1] http://lists.samba.org/archive/samba/2010-June/156708.html

Glenn Maynard

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