On 04/06/2016 10:05 PM, Huang Rui wrote:
On Wed, Apr 06, 2016 at 08:30:25AM -0700, Guenter Roeck wrote:
On Wed, Apr 06, 2016 at 03:44:11PM +0800, Huang Rui wrote:
+static void do_read_registers_on_cu(void *_data)
+{
+ struct fam15h_power_data *data = _data;
+ int cpu, cu;
+
+ cpu = smp_processor_id();
+
Is this function now defined in non-SMP code ? If so, can you point me to the
patch or branch introducing it ? It doesn't seem to be in mainline or in -next
unless I am missing it.
In include/linux/smp.h
#else /* !SMP */
static inline void smp_send_stop(void) { }
/*
* These macros fold the SMP functionality into a single CPU system
*/
#define raw_smp_processor_id() 0
...
/*
* smp_processor_id(): get the current CPU ID.
*
* if DEBUG_PREEMPT is enabled then we check whether it is
* used in a preemption-safe way. (smp_processor_id() is safe
* if it's used in a preemption-off critical section, or in
* a thread that is bound to the current CPU.)
*
* NOTE: raw_smp_processor_id() is for internal use only
* (smp_processor_id() is the preferred variant), but in rare
* instances it might also be used to turn off false positives
* (i.e. smp_processor_id() use that the debugging code reports but
* which use for some reason is legal). Don't use this to hack around
* the warning message, as your code might not work under PREEMPT.
*/
#ifdef CONFIG_DEBUG_PREEMPT
extern unsigned int debug_smp_processor_id(void);
# define smp_processor_id() debug_smp_processor_id()
#else
# define smp_processor_id() raw_smp_processor_id()
#endif
Actually smp_processor_id() should returns 0 if we disable CONFIG_SMP.
+ /*
+ * With the new x86 topology modelling, cpu core id actually
+ * is compute unit id.
+ */
+ cu = cpu_data(cpu).cpu_core_id;
+
+ rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR, &data->cu_acc_power[cu]);
+}
+
+/*
+ * This function is only able to be called when CPUID
+ * Fn8000_0007:EDX[12] is set.
+ */
+static int read_registers(struct fam15h_power_data *data)
+{
+ int this_cpu, ret, cpu;
+ int core, this_core;
+ cpumask_var_t mask;
+
+ ret = zalloc_cpumask_var(&mask, GFP_KERNEL);
+ if (!ret)
+ return -ENOMEM;
+
+ get_online_cpus();
+ this_cpu = smp_processor_id();
+
+ /*
+ * Choose the first online core of each compute unit, and then
+ * read their MSR value of power and ptsc in a single IPI,
+ * because the MSR value of CPU core represent the compute
+ * unit's.
+ */
+ core = -1;
+
+ for_each_online_cpu(cpu) {
+ this_core = topology_core_id(cpu);
+
+ if (this_core == core)
+ continue;
+
+ core = this_core;
+
Sorry if I missed some context - is it guaranteed that all cores in the same
compute unit are returned next to each other from for_each_online_cpu() ?
Yes, there is a documentation which introduced from v4.6-rc2:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f7be8610bca88e59dd2fd5d98fcbc5031ef0e079
- topology_core_id();
The ID of the core to which a thread belongs. It is also printed in
/proc/cpuinfo
"core_id."
...
AMD nomenclature for CMT systems:
[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
-> [Compute Unit Core 1] -> Linux CPU 1
-> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
-> [Compute Unit Core 1] -> Linux CPU 3
ray@hr-ub:~/tip$ cat /proc/cpuinfo | grep "core id"
core id : 0
core id : 0
core id : 1
core id : 1
"this_core" here actually means the [Compute Unit] id which current
[Compute Unit Core] belongs to. And "cpu" here means the [Compute Unit Core].
Ok, thanks.
Guenter
