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A set of updates for SMP function calls: 

- Improve localitu of smp_call_function_any() by utilizing
     sched_numa_find_nth_cpu() instead of picking a random CPU
 
   - Wait for work completion in smp_call_function_many_cond() only when
     there was actually work enqueued
 
   - Simplify functions by unutlizing the appropriate cpumask_*()
     interfaces
 
   - Trivial cleanups
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Merge tag 'smp-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull smp updates from Thomas Gleixner:
 "A set of updates for SMP function calls:

   - Improve locality of smp_call_function_any() by utilizing
     sched_numa_find_nth_cpu() instead of picking a random CPU

   - Wait for work completion in smp_call_function_many_cond() only when
     there was actually work enqueued

   - Simplify functions by unutlizing the appropriate cpumask_*()
     interfaces

   - Trivial cleanups"

* tag 'smp-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  smp: Wait only if work was enqueued
  smp: Defer check for local execution in smp_call_function_many_cond()
  smp: Use cpumask_any_but() in smp_call_function_many_cond()
  smp: Improve locality in smp_call_function_any()
  smp: Fix typo in comment for raw_smp_processor_id()
pull/1309/head
Linus Torvalds 2025-07-29 13:00:20 -07:00
parent dba3ec9f2a 946a728198
commit b34111a89f
2 changed files with 15 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/smp.h
View File

@ -234,7 +234,7 @@ static inline int get_boot_cpu_id(void)
#endif /* !SMP */
/**
* raw_processor_id() - get the current (unstable) CPU id
* raw_smp_processor_id() - get the current (unstable) CPU id
*
* For then you know what you are doing and need an unstable
* CPU id.

44
kernel/smp.c
View File

@ -741,32 +741,19 @@ EXPORT_SYMBOL_GPL(smp_call_function_single_async);
*
* Selection preference:
* 1) current cpu if in @mask
* 2) any cpu of current node if in @mask
* 3) any other online cpu in @mask
* 2) nearest cpu in @mask, based on NUMA topology
*/
int smp_call_function_any(const struct cpumask *mask,
smp_call_func_t func, void *info, int wait)
{
unsigned int cpu;
const struct cpumask *nodemask;
int ret;
/* Try for same CPU (cheapest) */
cpu = get_cpu();
if (cpumask_test_cpu(cpu, mask))
goto call;
if (!cpumask_test_cpu(cpu, mask))
cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));
/* Try for same node. */
nodemask = cpumask_of_node(cpu_to_node(cpu));
for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
cpu = cpumask_next_and(cpu, nodemask, mask)) {
if (cpu_online(cpu))
goto call;
}
/* Any online will do: smp_call_function_single handles nr_cpu_ids. */
cpu = cpumask_any_and(mask, cpu_online_mask);
call:
ret = smp_call_function_single(cpu, func, info, wait);
put_cpu();
return ret;
@ -792,7 +779,6 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
bool wait = scf_flags & SCF_WAIT;
int nr_cpus = 0;
bool run_remote = false;
bool run_local = false;
lockdep_assert_preemption_disabled();
@ -814,19 +800,8 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
*/
WARN_ON_ONCE(!in_task());
/* Check if we need local execution. */
if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) &&
(!cond_func || cond_func(this_cpu, info)))
run_local = true;
/* Check if we need remote execution, i.e., any CPU excluding this one. */
cpu = cpumask_first_and(mask, cpu_online_mask);
if (cpu == this_cpu)
cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
if (cpu < nr_cpu_ids)
run_remote = true;
if (run_remote) {
if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) {
cfd = this_cpu_ptr(&cfd_data);
cpumask_and(cfd->cpumask, mask, cpu_online_mask);
__cpumask_clear_cpu(this_cpu, cfd->cpumask);
@ -840,6 +815,9 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
continue;
}
/* Work is enqueued on a remote CPU. */
run_remote = true;
csd_lock(csd);
if (wait)
csd->node.u_flags |= CSD_TYPE_SYNC;
@ -851,6 +829,10 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
#endif
trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
/*
* Kick the remote CPU if this is the first work
* item enqueued.
*/
if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
nr_cpus++;
@ -869,7 +851,9 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
send_call_function_ipi_mask(cfd->cpumask_ipi);
}
if (run_local) {
/* Check if we need local execution. */
if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) &&
(!cond_func || cond_func(this_cpu, info))) {
unsigned long flags;
local_irq_save(flags);