Simultaneous upload and download hang about sshfs-win

[sganis]

This issue is recurrent. With all versions in different environments. When copying files, usually larger than 100MB, the copy operation hangs, and the only way to recover is killing the sshfs process. The drive becomes unresponsive during the hanging copy, too.
Is there a way to debug what is causing the hang?

[billziss-gh]

Try increasing the ThreadCount for your file system. It is likely that the file system is getting flooded with requests and does not have enough threads to deal with all of them timely.

The option is -o ThreadCount=N where N is the number of threads. The default is the number of cores in your machine (with a minimum of 2). So if you have 2 cores on your machine try running it with -o ThreadCount=4 or -o ThreadCount=8. (More threads should not harm performance, because of how WinFsp tells Windows to schedule threads, but I would not go over 100.)

BTW, for your scenario of transferring very large files you may also want to consider using the -o FileInfoTimeout and -o DirInfoTimeout options. Like so:

-o FileInfoTimeout=-1       # enable file caching
-o DirInfoTimeout=1000      # but keep dir caching at 1 sec to pick up remote changes

Be aware of cache coherency issues if you do use the last 2 options. For example, if a file is updated remotely, your local client may not "pick up" the changes until the file is closed. So I would not use this for an SSHFS server that has files updated by multiple clients.

[sganis]

None of suggested options solved the issue. When running with debug flag -d the copy does not hang but it is as slow as 1 MB/s. Removing the -d, the copy speed is 20 MB/s but hangs in the middle of the operation. Any idea how to debug what is causing the hang?. The file size is 1GB. I am working with the latest beta versions.

[billziss-gh]

This may be an SSHFS networking issue and unrelated to its file system layer where my expertise lies (SSHFS-Win simply packages libufse/sshfs and the required patches are now minimal as all necessary changes have been incorporated into the upstream project).

If you are able to debug C code, I would start with the vanilla libfuse/sshfs and build it on Cygwin (this is now possible with latest WinFsp).

[sganis]

I will try. Are you able to reproduce the problem?

…

On 21 Sep 2018, at 7:50 PM, Bill Zissimopoulos ***@***.***> wrote: This may be an SSHFS networking issue and unrelated to its file system layer where my expertise lies (SSHFS-Win simply packages libufse/sshfs and the required patches are now minimal as all necessary changes have been incorporated into the upstream project). If you are able to debug C code, I would start with the vanilla libfuse/sshfs and build it on Cygwin (this is now possible with latest WinFsp). — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.

[pavelxkrejci]

Try debugging on the SSH server. IIRC OpenSSH has at least 3 debugging levels.