On Tue, Aug 24, 2021, 09:50 Chris Roehrig <croeh...@house.org> wrote:
> I have a network of Windows, Linux and Mac machines and I use rsync to > synchronize various directories between them. > > I'm trying to figure out why my rsync transfers are so slow (<4 MB/s) only > when the remote endpoint is Cygwin rsync over sshd (with both a Linux or > Cygwin rsync client). In all other scenarios, I get the full 100MB/s as > expected from gigabit ethernet. This has been an ongoing problem for me > for a couple of years over several Windows and Cygwin versions, and I'd > like to try to fix it. > > If I run rsync --daemon --no-detach under mintty in the foreground on the > remote Windows endpoint, I get the full 100 MB/s transfers, so it seems > like it has something to do with rsync.exe running in the background under > the cygrunsrv+sshd service (which was installed normally using > ssh-host-config). > > If I do: > pv /dev/zero | ssh $WINHOST "cat > /dev/null" > or even > pv /dev/urandom | ssh $WINHOST md5sum > I also get the full 100 MB/s transfers, so it doesn't look like sshd > itself is being throttled by bandwidth or CPU. > > The machines have less than 15% CPU utilization while transferring, with > each of the 4 cores less than 30%, so it doesn't look to be CPU issue. > In Task Manager, sshd.exe and rsync.exe seem to be running normally using > only few percent CPU, and show Power Throttling=Disabled, Priority=Normal. > Setting their Priority to High doesn't seem to change things. > > Looking in Resource Monitor on the remote endpoint, the network usage is > pretty much a flat horizontal line at about 18 Mbps (2.5 MB/s), so it sure > looks to me as if rsync is somehow being bandwidth-throttled when run in > the background under cygsshd. > > It's almost as if rsync has an implicit --bwlimit override when it is run > from cygrunsrv+sshd (I've tried --bwlimit=0 on the client which makes no > difference). > > > Any ideas? Not sure where to go from here. > > Thanks, > -- Chris > > > Windows 10 v2004 (64-bit) > CYGWIN_NT-10.0 .... 3.2.0(0.340/5/3) 2021-03-29 08:42 x86_64 Cygwin > rsync version 3.2.4dev protocol version 31 > Linux Mint 20 > Older versions of windows had a setting to optimize the OS for either background services or foreground applications. One of the things this did was throttle network usage. I don't know if windows 10 has the same setting though. > -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
