Transmission uses 100% CPU on Ubuntu

[oneup]

Hi everyone,
I have discovered that transmission is using up 100% CPU on my ubuntu box.
I'm using Transmission 1.75 build 9117 on Ubuntu 9.10 Karmic Koala.
Here are some screenshots:

[phillipsjk]

You say that transmission is using 100% of the CPU, but you don't tell us what transmission is supposed to be doing while it is using the CPU. From the network activity I am going to guess you are sending/receiving files (torrents).

You may want to try the "top" utility for more detailed information about why a CPU is being held:

Code: Select all

Cpu(s): 46.8%us,  9.3%sy,  0.0%ni, 43.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
        User,    System,  Niced, Idle, Waiting for I/O, Hw IRQ,Soft Int., time "stolen" by hypervisor

Because the process is "sleeping" and using a nice round number of 100% of one core, I suspect your CPU is waiting for DMA transfers. This can be significant with heavy disk activity. (I have never seen it at 100% with a single CPU system though.) It is possible you network card uses DMA transfers as well.

During a DMA transfer, the device handles the copying of data to memory. The CPU is not allowed to touch the memory during this time (so has to sleep). It is still faster than the alternative where the CPU keeps polling the device for data.

[Jordan]

Could you please check and see if the high CPU load is reproducible in 1.80 beta 2?

[oneup]

You say that transmission is using 100% of the CPU, but you don't tell us what transmission is supposed to be doing while it is using the CPU. From the network activity I am going to guess you are sending/receiving files (torrents).

You may want to try the "top" utility for more detailed information about why a CPU is being held:

Code: Select all

Cpu(s): 46.8%us,  9.3%sy,  0.0%ni, 43.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
        User,    System,  Niced, Idle, Waiting for I/O, Hw IRQ,Soft Int., time "stolen" by hypervisor

Because the process is "sleeping" and using a nice round number of 100% of one core, I suspect your CPU is waiting for DMA transfers. This can be significant with heavy disk activity. (I have never seen it at 100% with a single CPU system though.) It is possible you network card uses DMA transfers as well.

During a DMA transfer, the device handles the copying of data to memory. The CPU is not allowed to touch the memory during this time (so has to sleep). It is still faster than the alternative where the CPU keeps polling the device for data.

I don't expect my BitTorrent client to use 100% CPU no matter what it's doing.

Could you please check and see if the high CPU load is reproducible in 1.80 beta 2?

Yes I'll try.

[oneup]

The problem is, this problem is hard to reproduce.
I think it happens after Transmission has been running for several days.
I'll install the 1.80 beta 2, leave it running for a few days and post the results.

[Jordan]

Is it an encrypted filesystem?

Is it an NTFS filesystem?

[oneup]

Ext4 filesystem. no encryption as far as I know.