Date: Sun, 29 Oct 2017 20:22:41 -0600 From: Ian Lepore <ian@freebsd.org> To: Peter Grehan <grehan@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r325108 - head/sys/amd64/vmm/io Message-ID: <1509330161.21609.86.camel@freebsd.org> In-Reply-To: <3b1ffc68-def3-04f6-2a1e-af44d6f3b4a5@freebsd.org> References: <201710292050.v9TKo3j5058456@repo.freebsd.org> <1509310495.21609.60.camel@freebsd.org> <3b1ffc68-def3-04f6-2a1e-af44d6f3b4a5@freebsd.org>
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On Sun, 2017-10-29 at 15:15 -0700, Peter Grehan wrote: > > > > > > > > Improve the performance of the hpet timer in bhyve guests by making the > > > timer frequency a power of two. This changes the frequency from 10 to > > > 16.7 MHz (2 ^ 24 HZ). Using a power of two avoids roundoff errors when > > > doing arithmetic in sbintime_t units. > > > > > > Testing shows this can fix erratic ntpd behavior in guests using the > > > hpet timer (which is the default for multicore guests). > > > > > > Reported by: bsam@ > > > > > > Modified: > > > head/sys/amd64/vmm/io/vhpet.c > In the future please respect MAINTAINERS and file a phab review for > code in this area. > > later, > > Peter. > > In fact I did check maintainers, and I just now checked it again, and seeing nothing on-point, wrote a really snarky reply. Luckily, before hitting send I realized you wouldn't have said anything unless there was an entry in there, so I checked like 4 more times before I noticed the line that begins vmm(4). I had been looking for a line that began with sys/amd64. So... sorry about that. Should I revert it and open a review? Longer-term, I was hoping to find some time over the next few weeks to further explore the roundoff errors in the timers and attempt a better fix, and I was definitely intending to put that up for review (especially because it involves math, and I'm always better off asking for help with that). -- Ian
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