Slow(er) download since 4.4.0, fluctuating speed

[adrian5]

qBittorrent & operating system versions

qBittorrent: 4.4.0
Operating system: Arch Linux
Qt: 6.2.2
libtorrent-rasterbar: 2.0.5.0

What is the problem?

Upgrading from 4.3.9 to 4.4.0, the achievable transfer speeds have decreased considerably. They now peak at around 2MiB/s, whereas double digits were easy before.

The download speed also fluctuates constantly (I think upload too, harder to find leeches):

This may or may not be related to:

#12336
#14867
#15495

Some select comments from the past 2 weeks in the qBittorrent reddit:

[Help] qBittorrent download speed decreases to almost zero after adding more than one torrent.

EDIT: Downgrading to 4.3.9 seemed to have fixed the problem, though I would still like to know why 4.4.0 all of a sudden crapped out on me

I've had a significant slow down in download & upload speeds

me too, I can't breach 1MB download speed. I'm getting irritated... maybe I should downgrade or use a new VPN service.

If you are using the version 4.4.0, the disk caching in the latest version of the libTorrent backend is really bad and many people are having problems. I have a gigabit connection and am trying to write to a platter disk, which means often my internet is faster than the drive can write, especially for large torrents which require a lot of disk seeking. Downgrade to 4.3.9 or earlier and you should see an improvement.

Solved my issues, downgrading to 4.3.9 made wonders! Thank you .. and for those who want to downgrade, easy mode: install the 4.3.9 over the 4.4.0 takes care of the problem, easy peasy. Oh man what a speed increase, sweet sweet speed.

Extremely slow download speed

I'm only getting less than 10kB/s out of torrents that usually run at 60MB/s. qbit connects to 40 (80) seeds and 50 (110) peers. I'm using the private internet access socks5 proxy with encryption, anonymous mode, and no upnp which worked really well until now.
I think it started when i updated to version 4.4.0, but a reinstal didn't help.

EDIT: Rolling back to 4.3.9 fixed the issue. Seems like there is some work to do by the qbit team.

I assume the developers are already aware, but didn't find a GitHub issue discussing recent speed issues in particular.

Steps to reproduce

No response

Additional context

• Picked torrent with hundreds of seeds
• Storage is fast
• 64GiB RAM

Log(s) & preferences file(s)

No response

[Disaer]

arvidn/libtorrent#6561

[peacey]

From my experience with QBT 4.4.0 and libtorrent 2.0.5, I'm able to reach and maintain 2.5 Gbps (line rate) perfectly fine as you can see from this 5 minute throughput graph. So it's strange you can't even get to double digits when I can get to triple. My CPU is only dual core and I only have 8 GB of RAM, also using Arch Linux.

The only thing I had to change with 2.0.5 is I had to reduce "File pool size" to 10 or 40, anything higher made my download throughput fluctuate too much (with libtorrent 1.x, a higher file pool size was not an issue).

[FaceCrap]

I see I'm not the only one that experienced the download speed going down to almost a crawl. I went from ~10MB/s to ~1.4MB/s and like the OP, reverting to 4.3.9 fixed that for me.

As suggested here and by peacey I tried setting file_pool_size to 10, but it didn't make any difference. FWIW, I usually only have 1 torrent actively downloading with at most 10 in seeding state

[lv-gh]

Confirming. 4.4.0 is useless (i wonder how the heck that crappy version got released?). UI just hangs (Not Responding; it starts responding again if i disconnect from internet), although it resumes downloads at slow speeds (~2 MB/s instead of ~20 MB/s@4.3.9). Windows 10, qBittorrent Portable 32 bit. How can i help narrowing down the problem? (logs, checks, steps?)

[falcon4fun]

Can confirm on 4.4.1.
I can suppose it's because of there is no any cache settings now.

Test case:
Network: 1 gbe connection
Storage: WD101EDBZ

Same torrents example. 4.3.9. No write cache overload. 2GB disk cache.
https://i.imgur.com/CVZN2XU.png

4.4.1. Spicky download. And write cache overload ~20-30% every some seconds.
https://i.imgur.com/M6LeW4a.png

Got back to 4.3.9 because I tryed to download UHD 60DB for 1H and got 10%, instead of download complete after 0.5H..

[adrian5]

For those finding this topic later on: The culprit appears to be (as Disaer pointed to) qBittorrent's migration from libtrorrent 1.2 to 2.0. The new version tries to do away with the old caching mechanism (deemed too complex and a maintenance burden for future development). The new approach – which outsources more of that to the OS – isn't ready for prime time.

In retrospect, qBittorrent should have stayed on 1.2 a bit longer, but 2.0 brings various new features so the desire to implement these is understandable. Personally, I don't know what to do for myself. I'm on a rolling release distro so I can't pin the qBittorrent package to an older version (along with its Qt5 dependencies). And AppImages only exist from 4.4.0 upwards.

[jokaorgua]

I can confirm that since 4.2.5 (for mac) the download speed is too slow. I take the same torrent file on version 4.4.* and get 2.5MB/s at max
I just switch to 4.2.5 and the download speed gets to my connection maximum of 11MB/s

This is a huge issue which lasts for a long time since version 4.2.5

[corobin]

I have also had crawling speeds for several versions now. I thought it was related to the other issue with SOCKS5 proxy not working properly, but maybe it's independent?

[adrian5]

I have also had crawling speeds for several versions now. I thought it was related to the other issue with SOCKS5 proxy not working properly, but maybe it's independent?

Different issues. The fluctuations stem from buffering issues in the client and occur in high traffic scenarios — they're not due to a lack of connectivity / seeds.

[nephtyss]

+1 Also experiencing very inconsistent speeds on v4.4.3.1

[jokaorgua]

@PriitUring how to understand which version of libtorrent am I using ?

macos 12.5
MacBook Pro m1 pro
Local ssd
Tried the most popular torrent with 2k seeds

[jokaorgua]

@PriitUring

libtorrent 2.0.7.0

I took the same torrent and compared versions 4.2.5 and 4.4.4
torrent with size of 26GB

when I used 4.2.5 everything was ok from the start until the end

with 4.4.4 the speed dropped once the torrent has reached 80%

app restart does not help. the issue still exists. maybe this is somehow connected to the size of the torrent?

[nephtyss]

@PriitUring

I found something interesting, the issue only happens when saving torrents to my NAS.
When saving to my machine's local NVMe drive, the download speed is as it should be :

However when setting the NAS as the destination :

Note that these tests were made using the latest version 4.4.4 with libtorrent v2.0.7.
Also, I had no speed issue when saving torrents on my NAS with 4.3.9.

Default settings? Yes
How many torrents? Made a test using a single active torrent
What OS? Linux Mint 21
How much RAM? 8GB
Torrents are downloaded to external drive, network drive, NVME, SSD or HDD? NAS
Same issue with both the latest libtorrent v1.2.17 and v2.0.7? Test was made using libtorrent v2.0.7
What if only downloading single popular torrent and everything else is paused, like the latest Ubuntu Linux ISO? Is latest qBittorrent with libtorrent v1.2.7 and v2.0.7 still slower than qBittorrent v4.3.9? That's the test I did

[chamby]

I found something interesting, the issue only happens when saving torrents to my NAS. When saving to my machine's local NVMe drive, the download speed is as it should be :

I am also experiencing this. The change to using memory mapped files is worse with libtorrent 2.0 on 4.4.x than libtorrent 1.2 on 4.4.x. This is for qBittorrent on Windows 10 saving directly to my Synology NAS. libtorrent 2.0 is causing blocking while the memory mapped write cache is flushing. Windows 10 may be to blame, but it is still a regression in experience from libtorrent 1.2. I end up with a download going full speed (gigabit) to download being fully choked while the write cache is flushed, over and over.

[adrian5]

@PriitUring I'll get back to you once my distro packages 4.4.4, which should be any day now. Alas, the AppImage doesn't come with a libtorrent v1.2 variant, so I cannot test that.

When I made this thread, I also tried writing to ramdisk to ensure there was no hardware/storage bottleneck. It's something about the new I/O mechanism causing unnecessary stalls, as @chamby said.

[adrian5]

@PriitUring I now have 4.4.4 and here are the results:

4.4.3 with libtorrent v2:

4.4.4 with libtorrent v2:

Clearly an improvement, but still strongly capped bandwidth. This would shoot up to 60 MiB/s with older libtorrent v1.2 releases.

[squaredcurves]

qBittorrent & operating system versions

qBittorrent: 4.4.0 Operating system: Arch Linux Qt: 6.2.2 libtorrent-rasterbar: 2.0.5.0

What is the problem?

Upgrading from 4.3.9 to 4.4.0, the achievable transfer speeds have decreased considerably. They now peak at around 2MiB/s, whereas double digits were easy before.

The download speed also fluctuates constantly (I think upload too, harder to find leeches):

This may or may not be related to:

#12336 #14867 #15495

Some select comments from the past 2 weeks in the qBittorrent reddit:

[Help] qBittorrent download speed decreases to almost zero after adding more than one torrent.

EDIT: Downgrading to 4.3.9 seemed to have fixed the problem, though I would still like to know why 4.4.0 all of a sudden crapped out on me

I've had a significant slow down in download & upload speeds

me too, I can't breach 1MB download speed. I'm getting irritated... maybe I should downgrade or use a new VPN service.

If you are using the version 4.4.0, the disk caching in the latest version of the libTorrent backend is really bad and many people are having problems. I have a gigabit connection and am trying to write to a platter disk, which means often my internet is faster than the drive can write, especially for large torrents which require a lot of disk seeking. Downgrade to 4.3.9 or earlier and you should see an improvement.

Solved my issues, downgrading to 4.3.9 made wonders! Thank you .. and for those who want to downgrade, easy mode: install the 4.3.9 over the 4.4.0 takes care of the problem, easy peasy. Oh man what a speed increase, sweet sweet speed.

Extremely slow download speed

I'm only getting less than 10kB/s out of torrents that usually run at 60MB/s. qbit connects to 40 (80) seeds and 50 (110) peers. I'm using the private internet access socks5 proxy with encryption, anonymous mode, and no upnp which worked really well until now.
I think it started when i updated to version 4.4.0, but a reinstal didn't help.
EDIT: Rolling back to 4.3.9 fixed the issue. Seems like there is some work to do by the qbit team.

I assume the developers are already aware, but didn't find a GitHub issue discussing recent speed issues in particular.

Steps to reproduce

No response

Additional context

• Picked torrent with hundreds of seeds
• Storage is fast
• 64GiB RAM

Log(s) & preferences file(s)

No response

This May be embarassing but go to preferences of Qbittorrent then click speed tab from left pane then you will see alternative rate limits section there you might see 10KBps or some other speed set for upload and downloads, just set both to zero. This immediately restored my 30MB/s(MBytes) speeds, this was my issue it might be yours as well.

[adrian5]

I'm well aware of the alternate speed limit (that's what I currently use to stabilize the jittery downloads), but thanks!

[adrian5]

Sorry for being so spammy in my own thread, but I wanted to inform the developers that the issue might have been resolved with 4.4.4. As observed in the 2nd screenshot, the problematic up-down behavior is gone, and I've gotten even better results (very steady speed) with another torrent.

I'm currently considering my VPN provider having QoS issues, which could explain the apparent bandwidth limit I'm hitting. Since I've been dealing with a hampered qBittorrent for months, I didn't even consider the network situation having changed in the background.

I'll test this in the coming days when I find the time and report back. Just wanted to give this feedback early.

[adrian5]

@PriitUring I did so yesterday with both v1.2 and v2.0 and hit the limits, but stably! (Same with 4.4.4 already from what I can tell). That prompted my earlier comment, but I wanted to keep things brief until I knew more.

I have now changed my VPN setup and that indeed was the reason for the upper limit!

Here 4.4.5 with the infamous, the accused, the cursed libtorrent 2.0:

---

So in conclusion: 4.4.4 fixed the rollercoaster I/O for which I opened this issue. You can now close it if you consider this done.

I hope the other users with I/O issues find a solution too, there were a few recent posts that reminded me of mine: #16765, #17123, #17608, #17609.

[chamby]

The download speed in v4.4.5 RC_2_0 does seem more stable with no seesawing behavior, but I have not confirmed that the throughput matches RC_1_2 yet. I will perform more testing and post a follow-up.

[ethankcvds]

I decided to try 4.5.0 with a new profile because when I updated from 4.3.9 I was still having download speed issues with both libtorrent 1.2 and 2.0. Something in the configuration from the previous install is causing issues for me when I upgraded.

[Jarsky]

Just updated from 4.3.9 to 4.5.0 and download speeds were completely broken. Like....0-50KB/s broken, to the point downloads stall. I switched from the default libtorrent 2.0 to the libtorrent 1.2 build of QBT 4.5.0 and it started working properly.

Ubuntu 22.04.1 LTS
Docker version 20.10.14

[ALEX8642]

Just updated from 4.3.9 to 4.5.0 and download speeds were completely broken. Like....0-50KB/s broken, to the point downloads stall. I switched from the default libtorrent 2.0 to the libtorrent 1.2 build of QBT 4.5.0 and it started working properly.

Ubuntu 22.04.1 LTS Docker version 20.10.14

I am having this issue no matter what I do with 4.5.0 with LT 1.2 AND 2.0.8.

If I start a torrent, HDD usage goes to 100% even though the torrent is practically stalled. It continues to do this for several minutes, after which hdd usage drops to a more normal number, and the download starts, but with incredibly random and massively fluctuating speeds. I was happy on 4.4.3 (used my entire connection ~1gbps - no problems) before it started causing BSOD's from filling up my RAM, so I updated. Not sure if related, but this is happening on different HDD's, seemingly no rhyme or reason for it, drive health is fine, no fragmentation, lots of room (I use Seagate EXOS X18 drives). I am really not sure what to do with Qbit. It seems to now behave this way no matter what I do, despite not making any changes to my system (WIN11 latest build, running Qbit 64 bit), LT 2.0.8 right now.

[ThatCoffeeGuy]

Same issue here, absolutely ridiculous speed fluctuating between 300kb and 6mb while I'm saving to a CMR HDD on a 1gbps network. Was this even tested at all?

Any still working torrent alternatives with webui?

[Jarsky]

@ALEX8642

You sure the issues you had on LT1.2 werent a different problem?

@ThatCoffeeGuy

If you use docker, I switched to this image which resolved the issue (using the older version of libTorrent).

version: "3.9"  
services:  
  qbittorrent:  
    image: lscr.io/linuxserver/qbittorrent:libtorrentv1-release-4.5.0_v1.2.18-ls7  
    container_name: qbittorrent  
    environment:  
      - PUID=1000  
      - PGID=1000  
      - TZ=America/Los_Angeles  
      - WEBUI_PORT=8080  
    volumes:  
      - /opt/qbittorrent/config:/config  
      - /mnt/downloads:/downloads  
    ports:  
      - 6881:6881  
      - 6881:6881/udp  
      - 8090:8080  
    restart: unless-stopped 

[ALEX8642]

@Jarsky

You sure the issues you had on LT1.2 werent a different problem?

As far as I know, I have the same behavior in both versions. If that was not the case, I would have switched to the one not doing this.

[lwouis]

Same here on macOS 13.2.1 and qBittorrent 4.5.2.

Here is the tooth-saw pattern I was getting with lt2:

I downloaded the same 4.5.2 with lt1, stopped qBittorrent lt2 and opened lt1. From that point, the pattern stopped and download speed is now stable.

Maybe related: #14594 (comment)

[emilyastranova]

@ALEX8642

You sure the issues you had on LT1.2 werent a different problem?

@ThatCoffeeGuy

If you use docker, I switched to this image which resolved the issue (using the older version of libTorrent).

version: "3.9"  
services:  
  qbittorrent:  
    image: lscr.io/linuxserver/qbittorrent:libtorrentv1-release-4.5.0_v1.2.18-ls7  
    container_name: qbittorrent  
    environment:  
      - PUID=1000  
      - PGID=1000  
      - TZ=America/Los_Angeles  
      - WEBUI_PORT=8080  
    volumes:  
      - /opt/qbittorrent/config:/config  
      - /mnt/downloads:/downloads  
    ports:  
      - 6881:6881  
      - 6881:6881/udp  
      - 8090:8080  
    restart: unless-stopped 

Appreciate this, got me back up and running.

[ghost]

Just updated from 4.3.9 to 4.5.0 and download speeds were completely broken. Like....0-50KB/s broken, to the point downloads stall. I switched from the default libtorrent 2.0 to the libtorrent 1.2 build of QBT 4.5.0 and it started working properly.
Ubuntu 22.04.1 LTS Docker version 20.10.14

I am having this issue no matter what I do with 4.5.0 with LT 1.2 AND 2.0.8.

If I start a torrent, HDD usage goes to 100% even though the torrent is practically stalled. It continues to do this for several minutes, after which hdd usage drops to a more normal number, and the download starts, but with incredibly random and massively fluctuating speeds. I was happy on 4.4.3 (used my entire connection ~1gbps - no problems) before it started causing BSOD's from filling up my RAM, so I updated. Not sure if related, but this is happening on different HDD's, seemingly no rhyme or reason for it, drive health is fine, no fragmentation, lots of room (I use Seagate EXOS X18 drives). I am really not sure what to do with Qbit. It seems to now behave this way no matter what I do, despite not making any changes to my system (WIN11 latest build, running Qbit 64 bit), LT 2.0.8 right now.

man, I had that on windows 10 and 7, on at least 4 different qbit versions (both libtorrent 1.2 and 2.0), on different HDD's, on different scenarios. It got me so madly annoyed I couldn't use it anymore. I experienced all of it: seesaw-like speeds, going from 0 to 1mb or so every 10-15 seconds, consistently slow speeds that didn't reflect my internet at all (only realized they were low after changing client), Qbit using 100% of my HDD for long periods of time, to the point only a restart solved it. the 100% disk issue happened for apparently no reason, and it would make the client hang on the "closing qbitorrent" for at least 15 minutes (most of the times as i've said that didn't reduce the usage, requiring a restart). I've tried everything: changing versions from 4.5.0 to 4.4.x to 4.3.9, enabling and disabling OS cache, running as admin, giving it more RAM, disabling vpn, everything.

I have no idea what kept causing those issues, as for quite a long time I had not experienced any issues with qbittorrent.