Messages in this thread | | | Subject | commit e9e9250b: sync wakeup bustage when waker is an RT task | From | Mike Galbraith <> | Date | Sat, 15 May 2010 13:57:08 +0200 |
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Hi Peter,
This commit excluded RT tasks from rq->load, was that intentional? The comment in struct rq states that load reflects *all* tasks, but since this commit, that's no longer true.
Looking at lmbench lat_udp in a PREEMPT_RT kernel, I noticed that wake_affine() is failing for sync wakeups when it should not. It's doing so because the waker in this case is an RT kernel thread (sirq-net-rx) - we subtract the sync waker's weight, when it was never added in the first place, resulting in this_load going gaga. End result is quite high latency numbers due to tasks jabbering cross-cache.
If the exclusion was intentional, I suppose I can do a waker class check in wake_affine() to fix it.
-Mike
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