From: Andi Kleen <[email protected]> For SMT specific workarounds it is useful to know if SMT is active on any online CPU in the system. This currently requires a loop over all online CPUs.
Add a global variable that is updated with the maximum number of smt threads on any CPU on online/offline, and use it for topology_max_smt_threads() The single call is easier to use than a loop. Not exported to user space because user space already can use the existing sibling interfaces to find this out. Signed-off-by: Andi Kleen <[email protected]> --- arch/x86/include/asm/topology.h | 5 +++++ arch/x86/kernel/smpboot.c | 24 ++++++++++++++++++++++++ 2 files changed, 29 insertions(+) diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index 7f991bd5031b..4707555f209e 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -129,6 +129,10 @@ extern const struct cpumask *cpu_coregroup_mask(int cpu); extern unsigned int __max_logical_packages; #define topology_max_packages() (__max_logical_packages) + +extern int max_smt_threads; +#define topology_max_smt_threads() max_smt_threads + int topology_update_package_map(unsigned int apicid, unsigned int cpu); extern int topology_phys_to_logical_pkg(unsigned int pkg); #else @@ -136,6 +140,7 @@ extern int topology_phys_to_logical_pkg(unsigned int pkg); static inline int topology_update_package_map(unsigned int apicid, unsigned int cpu) { return 0; } static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } +#define topology_max_smt_threads() 1 #endif static inline void arch_fix_phys_package_id(int num, u32 slot) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index a2065d3b3b39..6e5a721857f5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -105,6 +105,9 @@ static unsigned int max_physical_pkg_id __read_mostly; unsigned int __max_logical_packages __read_mostly; EXPORT_SYMBOL(__max_logical_packages); +/* Maximum number of SMT threads on any online core */ +int max_smt_threads __read_mostly; + static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip) { unsigned long flags; @@ -489,6 +492,7 @@ void set_cpu_sibling_map(int cpu) struct cpuinfo_x86 *c = &cpu_data(cpu); struct cpuinfo_x86 *o; int i; + int threads; cpumask_set_cpu(cpu, cpu_sibling_setup_mask); @@ -545,6 +549,10 @@ void set_cpu_sibling_map(int cpu) if (match_die(c, o) && !topology_same_node(c, o)) primarily_use_numa_for_topology(); } + + threads = cpumask_weight(topology_sibling_cpumask(cpu)); + if (threads > max_smt_threads) + max_smt_threads = threads; } /* maps the cpu to the sched domain representing multi-core */ @@ -1436,6 +1444,21 @@ __init void prefill_possible_map(void) #ifdef CONFIG_HOTPLUG_CPU +/* Recompute SMT state for all CPUs on offline */ +static void recompute_smt_state(void) +{ + int max_threads; + int cpu; + + max_threads = 0; + for_each_online_cpu (cpu) { + int threads = cpumask_weight(topology_sibling_cpumask(cpu)); + if (threads > max_threads) + max_threads = threads; + } + max_smt_threads = max_threads; +} + static void remove_siblinginfo(int cpu) { int sibling; @@ -1460,6 +1483,7 @@ static void remove_siblinginfo(int cpu) c->phys_proc_id = 0; c->cpu_core_id = 0; cpumask_clear_cpu(cpu, cpu_sibling_setup_mask); + recompute_smt_state(); } static void remove_cpu_from_maps(int cpu) -- 2.5.5
