Being a good Darwin citizen...
Being a good Darwin citizen...
- Subject: Being a good Darwin citizen...
- From: Shawn Erickson <email@hidden>
- Date: Wed, 3 Apr 2002 08:36:33 -0800
[sorry for the cross posting]
Over the last couple of months I have been seeing emails on the the
darwin developement lists from various developers regarding latency in
Darwin. It appears that they are finding some issue with latency when
using the normal IOKit methods. I personally never did get a clear
understand of what was causing the latency but it seems to be driving
people to do more work at direct interrupt time (more code going into
IOFilterInterruptEventSource::Filter) or for some skipping the use of
the IOKit provided workloops.
I personally see this as a dangerous trend for two main reasons (more
exist)...
1) Apple may have a issue in the kernel that needs to be fixed or
improved and people are coding around it instead of working with Apple
to resolved it.
2) More people doing stuff at direct interrupt time is going to cause
worse behavior for those following the generally accepted/specified
methods (using work loops and doing stuff at indirect interrupt or
better yet doing it in worker a thread). Direct interrupt time holds up
the entire system (I believe all processors). So spending much time here
can impact total system performance.
If we have people heading down this path we are going to have problems
IMHO. Basically if more people start hogging the system then others may
be forced to do the same.
Please only do stuff at direct interrupt time if no other way exists to
achieve what you need to do. AND.... do this ONLY after working with
Apple and/or the Darwin community to isolate the issue(s) you maybe
experiencing and if they can find no alternatives.
-Shawn
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