I will be implementing a power management strategy which will shutdown cpu's, so therefore in my situation it will have something to do with power management.
What do you exactly mean with "halt"? I suppose you are talking about gating the clock, right? Thomas On 5/9/07, Bart Smaalders <bart.smaalders at sun.com> wrote: > > Thomas De Schampheleire wrote: > > Hi, > > > > In cpu_offline() within uts/common/os/disp.c, there is a check on > > whether this is the last online : > > > > 1232 * Don't offline last online CPU in partition > > > > 1233 */ > > 1234 *if* (ncpus_online < > http://src.opensolaris.org/source/s?defs=ncpus_online> <= 1 || > > pp <http://src.opensolaris.org/source/s?defs=pp>->cp_ncpus < > http://src.opensolaris.org/source/s?defs=cp_ncpus> <= 1 || cpu_intr_count > <http://src.opensolaris.org/source/s?defs=cpu_intr_count>( > > cp <http://src.opensolaris.org/source/s?defs=cp>) < 2) > > 1235 *return* (EBUSY < > http://src.opensolaris.org/source/s?defs=EBUSY>); > > > > > > > > I am wondering why this check is actually there. If the last cpu can be > > offlined as well, then more energy can be saved. > > > > My first thoughts are that this is necessary in order to resume again > > when there is something to do. If none of the processors is online, who > > will execute the cpu_online() function. This would imply a certain > > wakeup interrupt that will wakeup a processor and starting its > > instructions at the cpu_online() function. This should be supported by > > hardware, which it probably isn't. Is this correct? > > > > Are there other reasons? > > > > Thanks, Thomas > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > laptop-discuss mailing list > > laptop-discuss at opensolaris.org > > The cpu_online/offline routines have nothing to do with power > management. These routines are used to disable CPUs that appear > to be developing faults, or need to be disabled for benchmarking > purposes. Note that Solaris halts idle cpus anyway. > > This might be better discussed in opensolaris-code.... > > - Bart > > > -- > Bart Smaalders Solaris Kernel Performance > barts at cyber.eng.sun.com http://blogs.sun.com/barts > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/laptop-discuss/attachments/20070509/0d8c779e/attachment.html>
