On 3/11/2021 11:53 AM, Liang, Kan wrote:
On 3/11/2021 11:09 AM, Peter Zijlstra wrote:
On Wed, Mar 10, 2021 at 08:37:56AM -0800, kan.li...@linux.intel.com
wrote:
From: Kan Liang <kan.li...@linux.intel.com>
Alder Lake Hybrid system has two different types of core, Golden Cove
core and Gracemont core. The Golden Cove core is registered to
"cpu_core" PMU. The Gracemont core is registered to "cpu_atom" PMU.
The difference between the two PMUs include:
- Number of GP and fixed counters
- Events
- The "cpu_core" PMU supports Topdown metrics.
The "cpu_atom" PMU supports PEBS-via-PT.
The "cpu_core" PMU is similar to the Sapphire Rapids PMU, but without
PMEM.
The "cpu_atom" PMU is similar to Tremont, but with different
event_constraints, extra_regs and number of counters.
+ /* Initialize big core specific PerfMon capabilities.*/
+ pmu = &x86_pmu.hybrid_pmu[X86_HYBRID_PMU_CORE_IDX];
+ pmu->name = "cpu_core";
+ /* Initialize Atom core specific PerfMon capabilities.*/
+ pmu = &x86_pmu.hybrid_pmu[X86_HYBRID_PMU_ATOM_IDX];
+ pmu->name = "cpu_atom";
So do these things use the same event lists as SPR and TNT?
No, there will be two new event lists on ADL. One is for Atom core, and
the other is for big core. They are different to SPR and TNT.
Is there any
way to discover that, because AFAICT /proc/cpuinfo will say every CPU
is 'Alderlake', and the above also doesn't give any clue.
Ricardo once submitted a patch to expose the CPU type under
/sys/devices/system/cpu, but I don't know the latest status.
https://lore.kernel.org/lkml/20201003011745.7768-5-ricardo.neri-calde...@linux.intel.com/
FWIW, ARM big.LITTLE does discriminate in its /proc/cpuinfo, but I'm not
entirely sure it's really useful. Mark said perf userspace uses
somethink akin to our CPUID, except exposed through sysfs, to find the
event lists.
Ah, I guess I misunderstood the concern. Let me try again.
Here is how perf tool find a event name via event list.
To get the correct event list file, yes, perf tool relies on the CPUID.
It will search a CPUID table in the
tools/perf/pmu-events/arch/x86/mapfile.csv.
GenuineIntel-6-97,v1,alderlake,core
Now perf tool knows the event list file "alderlake" is for the CPUID 97.
In the event list file for the Alder Lake (CPUID 0x97), we add a new
field "Unit" to distinguish the type of PMU.
"Unit": "cpu_core"
"Unit": "cpu_atom"
So perf can search the event name for a certain type of PMU via PMU name
"cpu_core" or "cpu_atom".
Perf tool doesn't use the "cpu_core/caps/pmu_name" for the event list.
Thanks,
Kan
