Re: [Xen-devel][PATCH] Change cpufreq_driver->get so that it can get other cpu's real physical freq

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 11/12/2008 04:15, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:

>> Above is a bad change where you kicks multiple cpus to update
>> same variable without any coordination. Also why can short path only
>> be used with strict condition that current cpu must be first bit in
>> mask? As long as current cpu is on mask, you can always read
>> directly.
> 
> No need any coordination here, please notice under whatever situation, there
> is only 1 bit set at cpumask here (we can only read the value of 1 cpu 1
> time).

Then please ASSERT(cpus_weight(cmd->mask) == 1) to make this constraint
clear.

> The first bit of cpumask here is not to set strict condition for short path.
> In fact, becuase of only 1 bit set at cpumask, the first_cpu() is only used to
> get its cpuid. If cpuid is the running cpu, go short path, otherwise go longer
> path.

The clearer (and faster) idiom is cpu_isset(smp_processor_id(), cmd->mask).

Please can you make these changes, test, and re-send.

 Thanks,
 Keir

> In fact, get_cur_val() was called by 2 paths (driver path and check_freq
> path), we design here is used to provide a unified interface to satisfied the
> requirement of both paths.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel