Date: Sat, 7 Nov 2015 22:26:06 +1100 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Ian Smith <smithi@nimnet.asn.au> Cc: Rasool Al-Saadi <ralsaadi@swin.edu.au>, Hans Petter Selasky <hps@selasky.org>, Luigi Rizzo <rizzo@iet.unipi.it>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Bruce Evans <brde@optusnet.com.au> Subject: RE: Timing issue with Dummynet on high kernel timer interrupt Message-ID: <20151107220450.X1692@besplex.bde.org> In-Reply-To: <20151107155144.I12989@sola.nimnet.asn.au> References: <6545444AE21C2749939E637E56594CEA3C0DCCC4@gsp-ex02.ds.swin.edu.au> <5638B7B5.3030802@selasky.org> <6545444AE21C2749939E637E56594CEA3C0DE7FF@gsp-ex02.ds.swin.edu.au> <563B2703.5080402@selasky.org> <6545444AE21C2749939E637E56594CEA3C0E0BD9@gsp-ex02.ds.swin.edu.au> <563C6864.2090907@selasky.org> <CA%2BhQ2%2Bhm2z0MkB-8w5xJM7%2Biz13r_ZjwmpZBnb30_D_48gaf-w@mail.gmail.com> <563C786C.1050305@selasky.org> <CA%2BhQ2%2Bj0WiGgzV119M1ZQiXP5Z7fq7deVxDPkOhvTc7hpTETKw@mail.gmail.com> <563CC186.9000807@selasky.org> <6545444AE21C2749939E637E56594CEA3C0E1B79@gsp-ex02.ds.swin.edu.au> <20151107155144.I12989@sola.nimnet.asn.au>
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On Sat, 7 Nov 2015, Ian Smith wrote: > ... > I also notice that with HPET, the timer interrupts themselves, whether > as few as 60-70/s idle in one-shot mode or ~2000/s in periodic, appear > in systat -vm or vmstat -w10 'Int' column, whereas with LAPIC or (yes I > even tried) i8254, these timer interrupts don't count in that column. Interrupt reporting is mostly broken for "fast" interrupts. E.g., systat -v counts them in the Interrupts column (separate and Total) but not in the Int summary; vmstat -m doesn't count them anywhere (it shows the Int summary). vmstat -i shows them much like the Interrupts column in systat -v (except it actually displays them all when there are too man CPUs or Interrupts to fit in systat -v). I use COUNT_IPIS and COUNT_XINVLTLB. The interrupts counted by these are actually fast. These mess up the systat -v display by giving too many active interrupts to display for just a couple of CPU. systat -v tends to display these in preference to more interesting interrupts. vmstat -i displays these too. "fast" and fast interrupts should be counted separately and are probaly best left out of the Int summary. They should also be displayed separately. > I'll try Hans' suggestion of adjusting in loader.conf, rebooting between > various options if really needed, though that'll be far more tedious .. > [ I've just now seen Bruce's latest, so maybe I haven't been doing the > wrong thing playing with these after all? ] The eventtimer choice is readonly, so rebooting seems to be required to change it. Too much like Windows. I often miss being able to change hz. Event timers now do much more complicated changes than that. They implement a sort of dynamic hz, but still use the boot-time hz as a default. Bruce
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