Date: Wed, 23 Jan 2013 08:20:52 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-stable@freebsd.org, Ian Lepore <ian@freebsd.org> Subject: Re: time issues and ZFS Message-ID: <CAJ-Vmon7pT6=UJ5ppRO_3SWRw-QM9W2Bz1=ffq2ovjxHGyOUrA@mail.gmail.com> In-Reply-To: <50FFFA8B.4040008@FreeBSD.org> References: <E1TxFcr-0006dx-MX@kabab.cs.huji.ac.il> <1358780588.32417.414.camel@revolution.hippie.lan> <E1TxJP2-000DS8-DJ@kabab.cs.huji.ac.il> <1358783667.32417.434.camel@revolution.hippie.lan> <CAJ-Vmo=2Dmf4Lb-uoUQDrybyRSS=_bnV5KcNYGg5MnMxfhhu7w@mail.gmail.com> <E1TxYHa-0002yo-4Y@kabab.cs.huji.ac.il> <CAJ-VmomdQORjs55ooW55Rgg0i1M13PPtnmCPRrp__btEWQz=4g@mail.gmail.com> <E1TxaZv-0005fj-5m@kabab.cs.huji.ac.il> <CAJ-VmokQbZFGmmy=KkEmP%2B7a6DQRGhdgupqF4sNCGJYxvA-B0g@mail.gmail.com> <50FFFA8B.4040008@FreeBSD.org>
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On 23 January 2013 06:58, Andriy Gapon <avg@freebsd.org> wrote: > I don't think that this is true of x86 hardware in general. > You might have hit some limitation or a quirk or a bug or an erratum for some > particular hardware. > > E.g. a chipset on this machine has a bit described as such: > "Set to 1 to skip the C state transition if there is break event > when entering C state." > The bit is set indeed and as far as I can tell the behavior matches the description. > > Most modern (non-embedded) machines seem to behave this way. Attempt to enter a > deeper C state while a break event is pending still incurs some overhead, but it's > not as bad as waiting for the next break event. I'll reverify the behaviour on my netbooks when I'm back home. It may be a quirk of an older 9.x, which is fixed in -HEAD. It may be a quirk of the older generation celeron hardware - in which case, we need to tell the user somehow.. Adrian
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