Abnormally slow IO performance on CIFS network share

[constantins2001]

qBittorrent & operating system versions

qBittorrent-nox: 4.5.4-r2 ARM64
Operating system: Ubuntu 22.04.2 LTS - Docker linuxserver/qbittorrent:4.5.4
Qt: 6.5.2-r0
libtorrent-rasterbar: 2.0.9-r2

What is the problem?

IO on mounted CIFS (SMB) network share are abnormally low.

• Downloading to the network share directly results in ~5.4 MB/s speeds.
• Downloading to local SSD results in speeds in excess of 26 MB/s
• Automatically moving to network share via qBittorrent results in about 5 MB/s speeds.
• Moving the file manually from local SSD to network share via the mv command results in speeds of ~35.7 MB/s.

This indicates qBittorrent has drastically slower speeds when moving downloads/downloading to network shares compared to a manual move operation.

Steps to reproduce

1. Mount CIFS share
   mount.cifs -o user=<XXX>,pass=<XXX>,cache=loose,actimeo=120,fsc //<URL>/<share> <mountpoint>
2. Set qBittorent download/move location to <mountpoint>
3. Download torrent
4. Observe performance impact

Additional context

I'll be happy to provide a full testing environment, just contact me directly.

Log(s) & preferences file(s)

No response

[stalkerok]

Try testing with libtorrent 1.2.19

[constantins2001]

Try testing with libtorrent 1.2.19

Big improvement. Used linuxserver/qbittorrent:libtorrentv1-version-release-4.5.4_v1.2.19 and was able to reach in excess of 12 MB/s direct download to network share.

[constantins2001]

When using libtorrent 1.2.19 my page cache just fills up due to the network share not being fast enough.
Normally this will freeze the entire machine once the kernel switches to sync writes and forces a reboot.

I configured the following sysctl options, now the system just hangs for a few seconds, but qBittorrent never recovers speed:

vm.min_free_kbytes = 120000
vm.dirty_background_ratio = 1
vm.dirty_ratio = 5

[86ed]

Why SMB in lieu of NFS?

[constantins2001]

My storage provider sadly only supports SMB (Hetzner Storage Box).
Partially due to the above issues I'll be moving to other means of storage soon, even tho price is unbeatable.

[constantins2001]

I'm now on a box with 2x 8 TB HDDs (HGST HUH721008AL) in RAID 0 and no longer experience a noticeable performance impact, contrary to some reports of others ( arvidn/libtorrent#7480 (comment) )

[luzpaz]

Anymore progress on this ?

[constantins2001]

Anymore progress on this ?

Sadly not. And I don't think there will be, as this seems to be a quite niche use case.

But as this isn't caused by qBittorrent directly, I recommend using the issue in the libtorrent repo for further comments: arvidn/libtorrent#7480

[luzpaz]

Closing in favor of upstream libtorrent ticket. @constantins2001 can you ping this ticket if any upstream changes take effect ?