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[Xen-devel] [PATCH/RFC] Wrong account for cpus other than 0 on hotplug

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>
  • Date: Fri, 13 Oct 2006 14:50:25 -0300
  • Delivery-date: Fri, 13 Oct 2006 10:50:33 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>


Is a x86_64 system with multiple CPUs, process accounting is done wrong after
one cpu goes off and on again (i.e.: a CPU bounded process is running
but gets 0% cpu for a time, until situation becomes normal again). 

The following patch is a first attempt to fix it. The struct keeps
zeroed after HYPERVISOR_vcpu_op() is called, thus leading to wrong
results. Accounting seems to be done right without it. However, I'm not
100 % sure we can just poke it out. Comments on this are very welcome.

Glauber de Oliveira Costa
Red Hat Inc.
"Free as in Freedom"
--- linux-2.6.18.x86_64/arch/i386/kernel/time-xen.c.orig        2006-10-13 
13:06:12.000000000 -0400
+++ linux-2.6.18.x86_64/arch/i386/kernel/time-xen.c     2006-10-13 
13:16:50.000000000 -0400
@@ -721,14 +721,8 @@ irqreturn_t timer_interrupt(int irq, voi
 static void init_missing_ticks_accounting(int cpu)
-       struct vcpu_register_runstate_memory_area area;
        struct vcpu_runstate_info *runstate = &per_cpu(runstate, cpu);
-       memset(runstate, 0, sizeof(*runstate));
-       area.addr.v = runstate;
-       HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu, &area);
        per_cpu(processed_blocked_time, cpu) =
        per_cpu(processed_stolen_time, cpu) =
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