Date: Fri, 30 Mar 2001 09:47:30 -0500 (EST) From: Andrew Gallatin <gallatin@cs.duke.edu> To: mjacob@feral.com Cc: freebsd-alpha@FreeBSD.ORG Subject: Re: do we care about performance yet? Message-ID: <15044.40066.746054.729549@grasshopper.cs.duke.edu> In-Reply-To: <Pine.BSF.4.21.0103292217330.6852-100000@beppo.feral.com> References: <15044.1867.943183.224703@grasshopper.cs.duke.edu> <Pine.BSF.4.21.0103292217330.6852-100000@beppo.feral.com>
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Matthew Jacob writes: > > Isn't this just basically saying you're i/o bound? Sorta. And user-space CPU bound as well. The lockmgr was a somewhat surprising standout (1.5% of the time doing a buildworld is spent in lockmgr). I'm thinking it would be interesting for people to occasionally profile the kernel after major infastructure changes & want to showcase what Iprobe can do (at less than 5% overhead, probably more like 1%). I profiled a buildworld because that's the "benchmark" people seem to care about. The netperf TCP streams are much more interesting. In the non witness case (http://www.cs.duke.edu/~gallatin/iprobe_current/netperf.120sec), ithread_loop() is at nearly 7% for a 100Mb TCP stream. Nearly all of that is assigned to the mtx_unlock_spin(&sched_lock) line at the bottom of the code. I haven't disassembled it, but I suspect that its just an effect of cache misses as we reschedule into the ithread loop. In the witness case, (http://www.cs.duke.edu/~gallatin/iprobe_current/netperf.witness.120sec) we see how expensive the witness functionality really is... Drew To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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