[PATCH 3/3] powerpc/smp: Cache CPU to chip lookup
From: Srikar Dronamraju <hidden>
Date: 2021-04-15 12:11:14
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
On systems with large CPUs per node, even with the filtered matching of related CPUs, there can be large number of calls to cpu_to_chip_id for the same CPU. For example with 4096 vCPU, 1 node QEMU configuration, with 4 threads per core, system could be see upto 1024 calls to cpu_to_chip_id() for the same CPU. On a given system, cpu_to_chip_id() for a given CPU would always return the same. Hence cache the result in a lookup table for use in subsequent calls. Since all CPUs sharing the same core will belong to the same chip, the lookup_table has an entry for one CPU per core. chip_id_lookup_table is not being freed and would be used on subsequent CPU online post CPU offline. Suggested-by: Michael Ellerman <mpe@ellerman.id.au> Cc: linuxppc-dev@lists.ozlabs.org Cc: qemu-ppc@nongnu.org Cc: Cedric Le Goater <clg@kaod.org> Cc: David Gibson <redacted> Cc: Nathan Lynch <redacted> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Valentin Schneider <redacted> Cc: Gautham R Shenoy <redacted> Reported-by: Daniel Henrique Barboza <redacted> Signed-off-by: Srikar Dronamraju <redacted> --- arch/powerpc/include/asm/smp.h | 1 + arch/powerpc/kernel/prom.c | 19 +++++++++++++++---- arch/powerpc/kernel/smp.c | 21 +++++++++++++++++++-- 3 files changed, 35 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 47081a9e13ca..03b3d010cbab 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h@@ -31,6 +31,7 @@ extern u32 *cpu_to_phys_id; extern bool coregroup_enabled; extern int cpu_to_chip_id(int cpu); +extern int *chip_id_lookup_table; #ifdef CONFIG_SMP
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 9a4797d1d40d..6d2e4a5bc471 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c@@ -65,6 +65,8 @@ #define DBG(fmt...) #endif +int *chip_id_lookup_table; + #ifdef CONFIG_PPC64 int __initdata iommu_is_off; int __initdata iommu_force_on;
@@ -914,13 +916,22 @@ EXPORT_SYMBOL(of_get_ibm_chip_id); int cpu_to_chip_id(int cpu) { struct device_node *np; + int ret = -1, idx; + + idx = cpu / threads_per_core; + if (chip_id_lookup_table && chip_id_lookup_table[idx] != -1) + return chip_id_lookup_table[idx]; np = of_get_cpu_node(cpu, NULL); - if (!np) - return -1; + if (np) { + ret = of_get_ibm_chip_id(np); + of_node_put(np); + + if (chip_id_lookup_table) + chip_id_lookup_table[idx] = ret; + } - of_node_put(np); - return of_get_ibm_chip_id(np); + return ret; } EXPORT_SYMBOL(cpu_to_chip_id);
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 5c7ce1d50631..50520fbea424 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c@@ -1073,6 +1073,20 @@ void __init smp_prepare_cpus(unsigned int max_cpus) cpu_smallcore_mask(boot_cpuid)); } + if (cpu_to_chip_id(boot_cpuid) != -1) { + int idx = num_possible_cpus() / threads_per_core; + + /* + * All threads of a core will all belong to the same core, + * chip_id_lookup_table will have one entry per core. + * Assumption: if boot_cpuid doesn't have a chip-id, then no + * other CPUs, will also not have chip-id. + */ + chip_id_lookup_table = kcalloc(idx, sizeof(int), GFP_KERNEL); + if (chip_id_lookup_table) + memset(chip_id_lookup_table, -1, sizeof(int) * idx); + } + if (smp_ops && smp_ops->probe) smp_ops->probe(); }
@@ -1468,8 +1482,8 @@ static void add_cpu_to_masks(int cpu) { struct cpumask *(*submask_fn)(int) = cpu_sibling_mask; int first_thread = cpu_first_thread_sibling(cpu); - int chip_id = cpu_to_chip_id(cpu); cpumask_var_t mask; + int chip_id = -1; bool ret; int i;
@@ -1492,7 +1506,10 @@ static void add_cpu_to_masks(int cpu) if (has_coregroup_support()) update_coregroup_mask(cpu, &mask); - if (chip_id == -1 || !ret) { + if (chip_id_lookup_table && ret) + chip_id = cpu_to_chip_id(cpu); + + if (chip_id == -1) { cpumask_copy(per_cpu(cpu_core_map, cpu), cpu_cpu_mask(cpu)); goto out; }
--
2.25.1