Re: [Xen-devel] [PATCH v9 3/6] x86: collect CQM information from all sockets

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.02.14 at 07:32, Dongxiao Xu <dongxiao.xu@xxxxxxxxx> wrote:
> +static void read_cqm_data(void *arg)
> +{
> +    uint64_t cqm_data;
> +    unsigned int rmid;
> +    int socket = cpu_to_socket(smp_processor_id());
> +    unsigned long i;
> +
> +    ASSERT(system_supports_cqm());
> +
> +    if ( socket < 0 )
> +        return;
> +
> +    for ( rmid = cqm->min_rmid; rmid <= cqm->max_rmid; rmid++ )
> +    {
> +        if ( cqm->rmid_to_dom[rmid] == DOMID_INVALID )
> +            continue;
> +
> +        wrmsr(MSR_IA32_QOSEVTSEL, QOS_MONITOR_EVTID_L3, rmid);
> +        rdmsrl(MSR_IA32_QMC, cqm_data);
> +
> +        i = (unsigned long)(cqm->max_rmid + 1) * socket + rmid;
> +        if ( !(cqm_data & IA32_QM_CTR_ERROR_MASK) )
> +            cqm->buffer[i] = cqm_data * cqm->upscaling_factor;

So my earlier comment regarding the NR_CPUS use in the allocation
of this buffer becomes even more relevant with the fact that you're
indexing by socket here, not by CPU - in that case, even nr_cpu_ids
is likely to be a gross overestimation.

> +static void select_socket_cpu(cpumask_t *cpu_bitmap)
> +{
> +    int i;
> +    unsigned int cpu;
> +    int socket, socket_curr = cpu_to_socket(smp_processor_id());
> +    DECLARE_BITMAP(sockets, NR_CPUS);

Please avoid putting a 4095-bit bitmap on the stack.

> +
> +    bitmap_zero(sockets, NR_CPUS);
> +    if (socket_curr >= 0)

Coding style.

Jan


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