Ah, so *that* is why the SANE GUI frontend I'm writing [1] pauses scanning and window events when it's using PIL to generate a thumbnail of the last page scanned, despite my use of deferToThread. A unit test I wrote with time.sleep() passed just fine, and I threw my hands up and walked away. Thanks for shedding light on what was very confusing and frustrating behavior. [1] spdf: "Scan to PDF," GPL. A Twisted-driven application with, shockingly, absolutely no networking. Coming soon to a download URL near you... --- Ed Suominen Registered Patent Agent Open-Source Software Author (yes, both...) Web Site: http://www.eepatents.com On Monday 14 March 2005 02:11 pm, twisted-python-request@twistedmatrix.com wrote:

My goal is somewhat similar in that I have multiple CPU's that aren't being used very much, but the other problem is that certain libraries I use (PIL) grab the GIL for long-running operations like image modifications. I can thread them off, but it still liberally acquires the GIL and makes the server unresponsive for the duration of the operation.