Date: Thu, 20 Dec 2012 12:13:42 +0100 From: =?ISO-8859-1?Q?Bernhard_Fr=F6hlich?= <decke@bluelife.at> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-emulation@freebsd.org, vbox@freebsd.org Subject: Re: issue with under-tick waits Message-ID: <CAE-m3X1V1Obi4UMVOTr%2BmeoNMXHv3WNvRa9N9XUtxCXsW-47xg@mail.gmail.com> In-Reply-To: <50C9D27C.1090707@FreeBSD.org> References: <50C9D27C.1090707@FreeBSD.org>
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On Thu, Dec 13, 2012 at 2:05 PM, Andriy Gapon <avg@freebsd.org> wrote: > > I think that the following patch is needed in VirtualBox 4.2.4 kernel module: > > --- sleepqueue-r0drv-freebsd.h.orig 2012-12-12 20:09:29.675203802 +0200 > +++ sleepqueue-r0drv-freebsd.h 2012-12-12 20:11:53.604203131 +0200 > @@ -82,6 +82,8 @@ > uint64_t cTicks = ASMMultU64ByU32DivByU32(uTimeout, hz, UINT32_C(1000000000)); > if (cTicks >= INT_MAX) > return RTSEMWAIT_FLAGS_INDEFINITE; > + else if (cTicks == 0 && uTimeout > 0) > + pWait->iTimeout = 1; > else > pWait->iTimeout = (int)cTicks; > #endif > > Without this patch any waits for periods shorter than a single tick return > immediately leading to a lot of unnecessary spinning. For example, I observe that > my guest's idle loop does a lot of sleeps with periods slightly shorter than 1 ms > (1/hz), e.g. 900us. All that waiting turns into pure spinning and VirtualBox eats > 100% of a core. > The above patch improves the situation significantly. Also, it (approximately) > follows what tvtohz does. Thanks a lot! I've added the patch to the port. https://github.com/decke/freebsd-vbox/commit/102a18dbfd8a0a668f7042e6d086b9d0df25e20f -- Bernhard Fröhlich http://www.bluelife.at/
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