Date: Sat, 17 Sep 2005 17:33:38 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: joseph.koshy@gmail.com Cc: current@freebsd.org Subject: Re: low(er) disk performance with sched_4bsd then with sched_ule Message-ID: <17196.35762.395155.325627@grasshopper.cs.duke.edu> In-Reply-To: <20050917102846.7bf26a56.lehmann@ans-netz.de> References: <20050914194612.15692485.lehmann@ans-netz.de> <20050914222013.178dc4dc.lehmann@ans-netz.de> <84dead72050914135239514c49@mail.gmail.com> <20050915000053.448f251b.lehmann@ans-netz.de> <84dead7205091500152a7c25d1@mail.gmail.com> <20050915172005.072f4bdf.lehmann@ans-netz.de> <20050915181238.54b16b4b.lehmann@ans-netz.de> <84dead720509160921732e7f96@mail.gmail.com> <20050916184911.38e2739a.lehmann@ans-netz.de> <20050916225219.73b53cd0.lehmann@ans-netz.de> <84dead7205091619435c12b528@mail.gmail.com> <20050917102846.7bf26a56.lehmann@ans-netz.de>
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Oliver Lehmann writes: > Joseph Koshy wrote: > > > ol> Wow, that update to BETA4 did the trick! While running > > ol> SCHED_4BSD: > > > > Fantastic! What is the profile like with the new 4BSD kernel? > > http://pofo.de/tmp/gprof.4bsd.3 I don't know the disk codepath very well, but the samples look a little suspect. We're copying a lot of data into and out of the kernel, so I would expect the majority of non disk wait time would be spent simply copying out the zero-filled pages, and copying them back in (AFAIK, dd uses read/write). Where is the time spent in read, write, uiomove, bcopy? What about ionode allocations, etc? And why do things like g_bsd_modify and g_bsd_ioctl rank so high? Aren't those only used when dealing with disklabels? BTW, I *love* that we've got access to the hw counters, and an easy way to do low-overhead profiling of the kernel. Drew
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