Russ Blaine
2007-Jun-29 22:41 UTC
[Xen-devel] create_periodic_time(): why forced to 0.9ms ?
create_periodic_time() forces the period to be at least 0.9 ms. Can anyone explain the history behind this? Why is this done, and how was this constant chosen? ----------------------------------------------------- Russ Blaine | Solaris Kernel | russell.blaine@sun.com _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Keir Fraser
2007-Jul-01 20:44 UTC
Re: [Xen-devel] create_periodic_time(): why forced to 0.9ms ?
That''s a question for whoever at Intel originally wrote that code. I''m sure the answer is that anything smaller is too small. :-) Which is kind of reasonable... -- Keir On 29/6/07 23:41, "Russ Blaine" <russell.blaine@sun.com> wrote:> create_periodic_time() forces the period to be at least 0.9 ms. Can anyone > explain the history behind this? Why is this done, and how was this constant > chosen? > > ----------------------------------------------------- > Russ Blaine | Solaris Kernel | russell.blaine@sun.com > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Zhai, Edwin
2007-Jul-02 05:33 UTC
Re: [Xen-devel] create_periodic_time(): why forced to 0.9ms ?
I''m not the original writer, but know some reason for this:) At the beginning, this logic is used for safe guard in case bad guest set too low freq in PIT channel. The lowest PIT freq we known that time is 1ms (linux 2.6 kernel) and allow some inaccuracy because of the round divide(%10, i.e 0.9 ms as you can see). On Sun, Jul 01, 2007 at 09:44:43PM +0100, Keir Fraser wrote:> That''s a question for whoever at Intel originally wrote that code. I''m sure > the answer is that anything smaller is too small. :-) Which is kind of > reasonable... > > -- Keir > > On 29/6/07 23:41, "Russ Blaine" <russell.blaine@sun.com> wrote: > > > create_periodic_time() forces the period to be at least 0.9 ms. Can anyone > > explain the history behind this? Why is this done, and how was this constant > > chosen? > > > > ----------------------------------------------------- > > Russ Blaine | Solaris Kernel | russell.blaine@sun.com > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xensource.com > > http://lists.xensource.com/xen-devel > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel >-- best rgds, edwin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel