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

[Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>]

Hi,

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) =
                runstate->time[RUNSTATE_blocked];
        per_cpu(processed_stolen_time, cpu) =

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