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Old 10-31-2017, 11:20 AM
SimonHF SimonHF is offline
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Join Date: Sep 2005
Posts: 44
120% CPU with OSX SecureCRT 8.1.4 ... how to fix?

I recently upgraded from SecureCRT 7.3.7 to 8.1.4 on OSX. I have 4 tabs open and SecureCRT is over 120% CPU. One tab is doing nothing and the two others are doing a light tail -f, and the last is running top. I noticed this because the laptop fan came on and was annoyingly loud.

If I ctrl-c the two tails and the top then the CPU usage stops.

If I start one of the tails then CPU usage hovers around 26% to 60%.

If I only start top then CPU usage hovers around 75% to 85%.

If I run only the following one-liner outputting 10 lines per second then CPU usage hovers around 90% to 120%:

$ perl -e 'use Time::HiRes; while(1){ printf qq[hello world!\n]; Time::HiRes::sleep(0.1); }'

If I leave the one-liner working and switch to another tab which is idle then CPU usage continues at the same rate.

If I modify the line for 10x more lines then the CPU usage stays the same.

If I modify the line for 10x less lines then the CPU usage hovers around 20% to 36%.

It doesn't seem to make any difference if the one-liner is run in a local shell tab or a remote shell tab.

FYI I'm running macOS Sierra Version 10.12.6 on a MacBook Pro (Retina, 15-inch, Mid 2014).

I tried running the same one-liner outputting 10 lines per second on SecureCRT 7.3.7 and CPU usage hovers around 60% if the tab is in focus and scrolling. If I switch to a different tab which isn't scrolling then CPU usage drops to about 6%.

I tried reducing the size of the tab to a quarter of the size on screen and CPU dropped to about 23% from 60%. Then I dragged the SecureCRT window from my external monitor onto the internal screen of the laptop and CPU dropped to about 16%. Dragging the same window onto the 2nd external monitor dropped the CPU usage to about 10%. This seems to match the order of display resolution with the first external monitor being biggest at 4K, internal display being second biggest retina resolution, and 2nd external monitor being the smallest.

Clearly the 8 version of SecureCRT is using up to double CPU than version 7 uses, and -- worse than that -- continues to chew on the CPU even if an idle tab is in focus.

Is this a known issue? Any ideas how to fix these new version 8 problems?

And any ideas how to lower the CPU usage for an active in focus tab on version 7?

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