Date: Thu, 31 May 2012 15:33:25 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-hackers@FreeBSD.org Cc: Adrian Chadd <adrian@FreeBSD.org>, Alexander Motin <mav@FreeBSD.org>, John Baldwin <jhb@FreeBSD.org> Subject: Re: ULE/sched issues on stable/9 - why isn't preemption occuring? Message-ID: <4FC76515.10302@FreeBSD.org> In-Reply-To: <CAJ-VmomU8mK5W%2BKrj4Mtn=3R=EcqPB-YDd9LwNxZo49%2By96bzA@mail.gmail.com> References: <CAJ-VmomWV2XibSNSr5Mfh7mpKsWrX5GKsNfU9iq7TO6%2BKxxQhw@mail.gmail.com> <201205301124.52597.jhb@freebsd.org> <CAJ-VmokXN9Ci8j2ExZkA-U=fsrMmeOn-ULB0pCYdtSwqHWpiKQ@mail.gmail.com> <CAJ-VmomU8mK5W%2BKrj4Mtn=3R=EcqPB-YDd9LwNxZo49%2By96bzA@mail.gmail.com>
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Sorry to hijack this thread, but just recently I've stumbled upon this Linux tool: http://lwn.net/Articles/353295/ perf sched latency seems to be particularly convenient and useful. The idea to track time between a point when a thread is waken up and a point when the thread actually run was quite good. I am sure that something like this could be scripted on top of ktr(4) using the trace points in the schedulers code. schedgraph is very cool, but it seems to lack some auto-analysis capabilities which would highlight the most interesting places. In this vein it might make sense to enable KTR and KTR_SCHED in GENERIC. -- Andriy Gapon
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