On 2013-7-29 17:38, Vincent Guittot wrote:
On 27 July 2013 12:42, Hanjun Guo hanjun.guo@linaro.org wrote:
In the cpu topology information, we define topology_physical_package_id() as cpu socket id, which means that the socket id is the idenfication for physical processor, not for a cluster in a cpu die.
On ARM64 platform, multi cluster in a cpu die will be normal, here is a example with 2 cores in a cluster and 2 cluster in a socket:
|--------------------------------------| | socket | | | | |---------------| |---------------| | | | cluster | | cluster | | | | | | | | | | |----| |----| | | |----| |----| | | | | |core| |core| | | |core| |core| | | | | |----| |----| | | |----| |----| | | | | | | | | | |---------------| |---------------| | | | |--------------------------------------|
ARM64 extended the MPIDR into 64 bit and introduce another affinity level, we can use this affinity level for socket id and use the third highest level affinity for cluster id, which make the socket id behavior in its original way.
Signed-off-by: Hanjun Guo hanjun.guo@linaro.org
arch/arm64/include/asm/topology.h | 1 + arch/arm64/kernel/topology.c | 8 ++++++-- 2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h index 8631808..ff68ecc 100644 --- a/arch/arm64/include/asm/topology.h +++ b/arch/arm64/include/asm/topology.h @@ -8,6 +8,7 @@ struct cputopo_arm64 { int thread_id; int core_id;
int cluster_id; int socket_id; cpumask_t thread_sibling; cpumask_t core_sibling;diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c index 1eb0435..6d1e5a6 100644 --- a/arch/arm64/kernel/topology.c +++ b/arch/arm64/kernel/topology.c @@ -80,12 +80,14 @@ void store_cpu_topology(unsigned int cpuid) /* core performance interdependency */ cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL_0(mpidr); cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL_1(mpidr);
cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL_2(mpidr);
cpuid_topo->cluster_id = MPIDR_AFFINITY_LEVEL_2(mpidr);cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL_3(mpidr);socket_id is currently used by update_siblings_masks to update the core_sibling mask. This mask defines which CPUs share their cache and AFAICT, the cache are shared at the cluster level so cluster_id should be used instead socket_id.
For some architecture, cpu cores in a cluster share L2 cache, and clusters in the cpu die share L3 cache, so I think we can make a difference between socket id and cluster id.
Have you got more information about the goal of this new level_3 ?
Actually not, I think ARM should give some recommendations as ARMv7 did.
Thanks Hanjun