Date: Tue, 26 Oct 2010 15:44:37 -0700 From: Nate Lawson <nate@root.org> To: Alexander Motin <mav@FreeBSD.org> Cc: acpi@freebsd.org, current@freebsd.org Subject: Re: Event based scheduling and USB. Message-ID: <4CC759D5.2020207@root.org> In-Reply-To: <4CC732C7.50409@FreeBSD.org> References: <201010261904.o9QJ4iwq089834@sana.init-main.com> <4CC732C7.50409@FreeBSD.org>
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On 10/26/2010 12:57 PM, Alexander Motin wrote: > Takanori Watanabe wrote: >> I updated my FreeBSD tree on laptop, to the current >> as of 18 Oct.2010, it works fine with CPU C3 state enabled, >> >> I think this is your achievement of event time scheduler, >> thanks! Ah, so mav@ implemented a tickless-scheduler? That is nice. >> But when USB driver is enabled, the load average is considerablly >> high (0.6 to 1.0) if sysctl oid kern.eventtimer.periodic is set to 0. >> Then kern.eventtimer.periodic is set to 1, the load average goes >> to 0 quickly as before, but almost never transit to C3. >> >> Is this behavior expected, or something wrong? The USB controller often keeps the bus mastering bit set. This keeps the system out of C3. The way to fix this is to implement global suspend. Put a device in suspend mode and then turn off power to the USB port it is on. Then the USB controller will stop polling the bus. >> I noticed one of usb host controller device shares HPET irq. >> When I implement interrupt filter in uhci driver, the load average >> goes to 0 as before. >> >> >> ==== >> % vmstat -i >> interrupt total rate >> irq1: atkbd0 398 2 >> irq9: acpi0 408 2 >> irq12: psm0 3 0 >> irq19: ehci1 37 0 >> irq20: hpet0 uhci0 35970 230 >> irq22: ehci0 2 0 >> irq256: em0 4 0 >> irq257: ahci0 1692 10 >> Total 38514 246 >> === > > I haven't noticed that issue and it is surely not expected for me. I > will try to reproduce it. > > Most likely you should be able to avoid interrupt sharing using some > additional HPET options, described at hpet(4). This seems silly. The whole point of APIC is to avoid clustering on a single interrupt but the BIOS put the timer on the USB controller irq? >> It's time to implement powertop for freebsd, isn't it? > > Surely it is. I was even thinking about possibility to port one from > OpenSolaris, but other work distracted me. You may take it, it you wish. It seems worth doing the internals new, but maybe outputting information in a compatible format for reporting tools. -- Nate
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