renegade-project/linux-next
2
0
Fork 0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-22 12:14:01 +08:00
Code

powerpc/smp: Cache CPU to chip lookup

Browse Source 
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.

Reported-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210415120934.232271-4-srikar@linux.vnet.ibm.com
This commit is contained in:
Srikar Dronamraju 2021-04-15 17:39:34 +05:30 committed by Michael Ellerman
parent 131c82b6a1
commit c1e53367da
3 changed files with 35 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/smp.h
View File

@ -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

19
arch/powerpc/kernel/prom.c
View File

@ -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);
of_node_put(np);
return of_get_ibm_chip_id(np);
if (chip_id_lookup_table)
chip_id_lookup_table[idx] = ret;
}
return ret;
}
EXPORT_SYMBOL(cpu_to_chip_id);

21
arch/powerpc/kernel/smp.c
View File

@ -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;
}