[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL
>From: Jeremy Fitzhardinge >Sent: 2009年8月5日 8:06 > >On 07/24/09 01:04, Keir Fraser wrote: >> Okay, so the issue you are worried about is not specific to >Xen. So how is >> native Linux tackling this, for example? >> > >Linux will use the tsc where possible, but regularly assesses its >perceived accuracy and will move to a different clocksource if the tsc >appears to the playing up. I don't think it ever assumes the tsc is >synced between CPU/cores. It cares. See tsc_sync.c under x86 arch, where unsynced warps mark tsc as unstable. Thanks, Kevin > >It allows rdtsc from usermode, but it is generally considered >to be very >buggy and ill-defined behaviour. It makes no attempt to make usermode >rdtsc in any way meaningful. The exception is the vgettimeofday >vsyscall which does Xen-like timekeeping, in which it gets the tsc,cpu >tuple atomically, then scales it with timing parameters from >the kernel. > > J > >_______________________________________________ >Xen-devel mailing list >Xen-devel@xxxxxxxxxxxxxxxxxxx >http://lists.xensource.com/xen-devel > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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