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rcuscale: Measure grace-period kthread CPU time

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This commit adds the ability to output the CPU time consumed by the
grace-period kthread for the RCU variant under test.  The CPU time is
whatever is in the designated task's current->stime field, and thus is
controlled by whatever CPU-time accounting scheme is in effect.

This output appears in microseconds as follows on the console:

rcu_scale: Grace-period kthread CPU time: 42367.037

[ paulmck: Apply feedback from Stephen Rothwell and kernel test robot. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
This commit is contained in:
Paul E. McKenney 2023-05-17 05:01:28 -07:00
parent bb7bad3dae
commit 5f8e320269
3 changed files with 28 additions and 0 deletions
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1
include/linux/rcupdate_trace.h
View File

@ -87,6 +87,7 @@ static inline void rcu_read_unlock_trace(void)
void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
void synchronize_rcu_tasks_trace(void);
void rcu_barrier_tasks_trace(void);
struct task_struct *get_rcu_tasks_trace_gp_kthread(void);
#else
/*
* The BPF JIT forms these addresses even when it doesn't call these

21
kernel/rcu/rcuscale.c
View File

@ -141,6 +141,7 @@ struct rcu_scale_ops {
void (*gp_barrier)(void);
void (*sync)(void);
void (*exp_sync)(void);
struct task_struct *(*rso_gp_kthread)(void);
const char *name;
};
@ -336,6 +337,7 @@ static struct rcu_scale_ops tasks_tracing_ops = {
.gp_barrier = rcu_barrier_tasks_trace,
.sync = synchronize_rcu_tasks_trace,
.exp_sync = synchronize_rcu_tasks_trace,
.rso_gp_kthread = get_rcu_tasks_trace_gp_kthread,
.name = "tasks-tracing"
};
@ -563,6 +565,8 @@ static struct task_struct **kfree_reader_tasks;
static int kfree_nrealthreads;
static atomic_t n_kfree_scale_thread_started;
static atomic_t n_kfree_scale_thread_ended;
static struct task_struct *kthread_tp;
static u64 kthread_stime;
struct kfree_obj {
char kfree_obj[8];
@ -808,6 +812,18 @@ rcu_scale_cleanup(void)
if (gp_exp && gp_async)
SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");
// If built-in, just report all of the GP kthread's CPU time.
if (IS_BUILTIN(CONFIG_RCU_SCALE_TEST) && !kthread_tp && cur_ops->rso_gp_kthread)
kthread_tp = cur_ops->rso_gp_kthread();
if (kthread_tp) {
u32 ns;
u64 us;
kthread_stime = kthread_tp->stime - kthread_stime;
us = div_u64_rem(kthread_stime, 1000, &ns);
pr_info("rcu_scale: Grace-period kthread CPU time: %llu.%03u us\n", us, ns);
show_rcu_gp_kthreads();
}
if (kfree_rcu_test) {
kfree_scale_cleanup();
return;
@ -921,6 +937,11 @@ rcu_scale_init(void)
if (cur_ops->init)
cur_ops->init();
if (cur_ops->rso_gp_kthread) {
kthread_tp = cur_ops->rso_gp_kthread();
if (kthread_tp)
kthread_stime = kthread_tp->stime;
}
if (kfree_rcu_test)
return kfree_scale_init();

6
kernel/rcu/tasks.h
View File

@ -1830,6 +1830,12 @@ void show_rcu_tasks_trace_gp_kthread(void)
EXPORT_SYMBOL_GPL(show_rcu_tasks_trace_gp_kthread);
#endif // !defined(CONFIG_TINY_RCU)
struct task_struct *get_rcu_tasks_trace_gp_kthread(void)
{
return rcu_tasks_trace.kthread_ptr;
}
EXPORT_SYMBOL_GPL(get_rcu_tasks_trace_gp_kthread);
#else /* #ifdef CONFIG_TASKS_TRACE_RCU */
static void exit_tasks_rcu_finish_trace(struct task_struct *t) { }
#endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */