Re: [RFC][PATCH 00/32] Nohz cpusets v2 (adaptive tickless kernel)

[Gilad Ben-Yossef]

On Tue, Mar 27, 2012 at 6:22 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
> On Tue, 27 Mar 2012, Gilad Ben-Yossef wrote:
>
>> +static void vmstat_update(struct work_struct *w)
>> +{
>> +     int cpu, this_cpu = smp_processor_id();
>> +     int sleepy_cpu_counter = 0;
>> +     static spinlock_t lock;
>> +
>> +     if(spin_trylock(&lock)) {
>
> Trylock would cause cache bouncing between vmstat runs on various
> processors. The reason that vmstat_update exists is to avoid these cache
> bounces. Please no exclusive cacheline acquisiton by all cpus by default.
>

Right, I didn't think of that.

> The best method would be to assign a sacrifical lamb cpu and check if we
> are running on that cpu. That way taking a lock can be avoided.

Cool, I'll do it.

Thanks

Gilad


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