[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL
On 27/07/2009 18:25, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote: >> I believe this affects the guest OS executing RDTSC, not >> guest apps, and is >> only to delay the TSC to not 'run past' pending timer ticks >> (typically where >> they have been delayed due to the guest being preempted). >> >> -- Keir > > Could be. The text would lead me to believe otherwise > though. Read the section on "Virtual TSC" in the > above PDF. Specifically the Virtual TSC "advances even > when the the virtual CPU is not running" and "In the > past, this feature had sometimes been recommended to > improve performance of APPLICATIONS that read the > TSC frequently..." (my emphasis) Yes, then it sounds like they virtualise it for apps too. Also there is an option to virtualise the TSC at a specified frequency -- that would be pretty weird if it applied only to guest-OS RDTSCs but not guest-app RDTSCs. Interesting... -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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