Messages in this thread | | | Date | Sat, 3 Aug 2002 13:38:24 +0200 (CEST) | From | Ingo Molnar <> | Subject | context switch vs. signal delivery [was: Re: Accelerating user mode linux] |
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On 2 Aug 2002, Alan Cox wrote:
> The numbers look very different on a real processor. Signal delivery is > indeed not stunningly fast but relative to a context switch its very low > indeed.
actually the opposite is true, on a 2.2 GHz P4:
$ ./lat_sig catch Signal handler overhead: 3.091 microseconds
$ ./lat_ctx -s 0 2 2 0.90
ie. *process to process* context switches are 3.4 times faster than signal delivery. Ie. we can switch to a helper thread and back, and still be faster than a *single* signal.
signals are in essence 'lightweight' threads created and destroyed for the purpose of a single asynchronous event, it's IMO a very inefficient and baroque concept for almost anything (but debugging and a number of very special uses). I'd guess that with a sane threading library a helper thread is faster for almost everything.
Ingo
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