Call for TESTING (was Re: [1.7.0-50] scp progress counter flies through first 175 MB or so)
Corinna Vinschen
corinna-cygwin@cygwin.com
Tue Jun 30 14:35:00 GMT 2009
On Jun 29 12:59, Warren Young wrote:
> I scp'd a 1.6 GB file back and forth to a Linux server over GigE to a
> fast new RAID-10. I tested 1.7.0-50 and 20090629.
>
> Results:
>
> On a 32-bit XP box, 1.7.0-50 gives about 15 MByte/sec for both upload
> and download. (This box can't really hit GigE speeds due to crappy
> cabling and a low-quality switch.) On switching to the snapshot, the
> download speed is about the same, but upload is cut to 4-5 MB/sec.
>
> On a 64-bit Vista box, 1.7.0-50 gives inconsistent behavior. Download
> behaves as it should: ~45 MB/sec here, due to better switch and cabling.
> But, uploading with scp gives the reported behavior: the scp status
> fills out to 100% very fast but then scp doesn't finish running for
> quite a while. It's like it's buffering a big fraction of the 1.6 GB,
> which isn't impossible, since this box has 12 GB of RAM. (Core i7,
> DDR3, wheee!)
>
> After switching to the snapshot on that Vista-64 box, the scp progress
> display becomes useful, growing steadily as scp runs. Unfortunately, my
> upload speed is down to around 5 MB/sec here, just as on the XP box.
>
> A different non-Cygwin scp client I have here can manage much faster
> transfer speeds, so I can rule out disk and network bottlenecks. The
> slowdowns are in Cygwin itself or the Cygwin scp port.
>
> I can rule out a problem in the general network I/O handling: changing
> the DLL doesn't seem to affect ttcp results materially. It's either scp
> or the way scp uses cygwin1.dll.
I just had a look into this and I think I found a way to raise the
outbound transfer rates somewhat. The outbound speed is always slower
than the inbound speed, no matter what I try. However, I'm now at a
point where it might be more acceptable.
One of my test machines, a 2K8 32 bit box has the following scp
transfer rates under 1.5.25:
inbound: 17.2 MB/s
outbound: 3.5 MB/s
With the latest snapshot:
inbound: 21.5 MB/s
outbound: 4.2 MB/s
With the latest from CVS:
inbound: 21.5 MB/s
outbound: 11.5 MB/s
What's still not clear is why the ssh process takes so much CPU.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
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