RE: [Xen-ia64-devel] [PATCH] Fix smp_processor_id for host SMP

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Committed. 

> -----Original Message-----
> From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf 
> Of Tian, Kevin
> Sent: Monday, December 19, 2005 9:42 PM
> To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-ia64-devel] [PATCH] Fix smp_processor_id for host SMP
> 
> Fix smp_processor_id to be linked to correct processor id under vcpu,
> which is the exact one updated by scheduler. Or else easy to think how
> things get messed under SMP environment. One phenomenon observed is
> about softirq. Exit path on CPU1 checks pending indicator by
> local_cpu_data, and then goto do_softirq if pending true. However
> do_softirq uses cpu_data(cpu) to query pending bit again. Cpu index is
> aquired from smp_processor_id, with thread_info->cpu not cared by
> scheduler. Finally do_softirq on CPU1 tries to operate percpu data on
> CPU0 then.
> 
> Also disable several prints within critical path, like 
> sending IPI. Due
> to slow serial speed, this will slow down overall performance heavily
> since event channels among CPUs are in traffic.
> 
> This patch is critical for host SMP.
> 
> Signed-off-by Kevin Tian <kevin.tian@xxxxxxxxx>
> 
> Thanks,
> Kevin
> 

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