camera_calibration: Fix excessive CPU usage due to queue synchronization #432
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Fixes excessive (up to 100%) CPU usage caused by queue synchronization code. The new, modified Queue class BufferQueue drops the oldest item when adding to a full queue. This is identical to deque's behavior, but adds the much more CPU-efficient thread synchronization mechanism of Queue.
SteveMacenski
approved these changes
Jul 18, 2019
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JWhitleyWork
approved these changes
Jul 18, 2019
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(I do love some shipping graphics) |
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I was getting near 100% CPU usage with cameracalibrator.py even if no images (after then inital one) are being received and no actual processing is taking place.
This appeared to be caused by the queue synchronization code doing
to wait for incoming images. This does not look too unreasonable, but replacing it with proper thread synchronization via locks fixed the excessive CPU usage.
Specifically, I replaced the deque with a slightly modified standard Queue that drops the oldest item instead of raising an exception when adding an item to an already full queue, just like deque. Queue also uses deque internally anyway, so in that sense the performance should be the same.
I also added a
--queue-sizeparameter to allow adjustment of the max queue size. I found this useful when calibrating with images from a bag, where you want to use all available frames and set the playback rate as high as possible.Relates to #112 and #121.