CPU usage spikes to 100% when receiving a lot of text over ssh

By LaladeLausa... on September 02, 2010 19:58 (imported from Google Code)

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What steps will reproduce the problem?

1. login somewhere via ssh
2. run any script which run apps on multiple machines and redirects output to terminal.
3. apps should generate a lot of output. Output is around 200-6000 lines of code per second, withe 4 apps running in parallel.
4. observe CPU usage on Mac

What is the expected output? What do you see instead?
- I expect more stable CPU usage. Old version was much better with that regard.

What version of the product are you using? On what operating system?
alpha6 on MacBook Pro2,1; Mac OS X 10.6.4

PS. If I change focus to another tab, CPU usage is much lower, without spikes.

Please provide any additional information below.

Comment 1 by gnach... on September 02, 2010 21:13

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Thank you for the bug report. Is the performance worse than previous alphas, or worse than the original iTerm? Also, if you can perform these steps it will help to determine the cause of the slowness on your system:

1. Open /Applications/Utilities/Activity Monitor
2. Select iTerm in the process list
3. Click the "Sample Process" button in the Activit Monitor toolbar
4. A progress bar will display and then a window of text will open.
5. Copy the text into this bug (or save it and add it as an attachment).

Thanks,
George

Comment 2 by LaladeLausa... on September 03, 2010 13:59

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Hi George,

I was comparing the iTerm2 with the original iTerm (alpha6 was the first version of the iTerm2 I found).

Here are the sample of iTerm2 under described workload. Version is alpha6. The 'fronttab' is a sample of iTerm2 when output is happening in the front tab, while the other file is when output is in another tab.

Hope it helps.

Comment 3 by gnach... on September 05, 2010 20:10

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What version of the old iTerm were you running? When I sample iTerm 0.10 I get almost the same profile as what you posted. You can mitigate the problem by adjusting the display refresh rate.

Also, is the complaint that iTerm2 is using 100% of CPU or that utilisation is different between active and inactive tabs?

Comment 4 by LaladeLausa... on September 09, 2010 09:43

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Hi, I was running the last version (0.10) of old iTerm. The refresh rate was the same for both versions (at least sliders were at the same position).

My main complaint is that iTerm2 uses more CPU than old iTerm. Not 100% all the time, but still more. Utilization is different between active and inactive tabs, but that is to expect, since active tabs need to draw new data more frequently.

Comment 5 by gnach... on September 18, 2010 23:29

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Confirmed. Using this script:

for iTerm 0.10:
1.914u 1.741s 0:09.02 40.4% 0+0k 0+0io 0pf+0w

for iTerm at r144:
1.899u 1.710s 0:17.88 20.1% 0+0k 0+0io 0pf+0w

for Terminal on Snow Leopard:
1.891u 1.241s 0:06.98 44.8% 0+0k 0+0io 0pf+0w

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[iterm 0.10 spam sample.txt](https://storage.googleapis.com/google-code-attachments/iterm2/issue-39/comment-5/iterm 0.10 spam sample.txt)

[iterm2 spam.rtf](https://storage.googleapis.com/google-code-attachments/iterm2/issue-39/comment-5/iterm2 spam.rtf)

Comment 6 by gnach... on September 19, 2010 07:13

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Not quite as fast as iTerm 0.10 but much faster than before. There's a bit more blood that can be squeezed, but it'll be tricky.

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Status: Fixed