Merge "sched: Provide an easy method to log context switch latencies" (c44483c3) · Commits · e / devices / android_kernel_sony_msm8994

arch/arm64/Kconfig

+6 −0

Original line number	Diff line number	Diff line
		@@ -344,6 +344,12 @@ config SCHED_SMT
		MultiThreading at a cost of slightly increased overhead in some
		places. If unsure say N here.

		config ARCH_WANTS_CTXSW_LOGGING
		bool "Enable logging in context switch"
		depends on SMP
		help
		Logs critical context switch latencies. If unsure say N here.

		config NR_CPUS
		int "Maximum number of CPUs (2-32)"
		range 2 32

kernel/sched/core.c

+53 −0

Original line number	Diff line number	Diff line
		@@ -90,6 +90,30 @@
		#define CREATE_TRACE_POINTS
		#include <trace/events/sched.h>

		#include <soc/qcom/watchdog.h>

		#define DLOG_SIZE 15000
		#define MAX_CTXSW_LATENCY 1000000000
		static DEFINE_PER_CPU(char[DLOG_SIZE], dbuf);
		static DEFINE_PER_CPU(char *, dptr);

		#define dlog(x...) \
		do { \
		unsigned long dflags; \
		char ptr, buf; \
		int dcpu; \
		local_irq_save(dflags); \
		dcpu = smp_processor_id(); \
		buf = per_cpu(dbuf, dcpu); \
		ptr = per_cpu(dptr, dcpu); \
		ptr += snprintf(ptr, 10, "CPU %d ", dcpu); \
		ptr += snprintf(ptr, 490, x); \
		if (ptr - buf > DLOG_SIZE - 500) \
		ptr = buf; \
		per_cpu(dptr, dcpu) = ptr; \
		local_irq_restore(dflags); \
		} while (0)

		const char *task_event_names[] = {"PUT_PREV_TASK", "PICK_NEXT_TASK",
		"TASK_WAKE", "TASK_MIGRATE", "TASK_UPDATE",
		"IRQ_UPDATE"};
		@@ -3444,6 +3468,9 @@ prepare_task_switch(struct rq rq, struct task_struct prev,
		struct task_struct *next)
		{
		trace_sched_switch(prev, next);
		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		dlog("%s: end trace at %llu\n", __func__, sched_clock());
		#endif
		sched_info_switch(prev, next);
		perf_event_task_sched_out(prev, next);
		fire_sched_out_preempt_notifiers(prev, next);
		@@ -3577,11 +3604,19 @@ context_switch(struct rq rq, struct task_struct prev,
		struct task_struct *next)
		{
		struct mm_struct mm, oldmm;
		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		u64 start, end;
		#endif

		prepare_task_switch(rq, prev, next);

		mm = next->mm;
		oldmm = prev->active_mm;

		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		start = sched_clock();
		dlog("%s: n_mm: %p, finish pts at %llu\n", __func__, mm, start);
		#endif
		/*
		* For paravirt, this is coupled with an exit in switch_to to
		* combine the page table reload and the switch backend into
		@@ -3600,6 +3635,15 @@ context_switch(struct rq rq, struct task_struct prev,
		prev->active_mm = NULL;
		rq->prev_mm = oldmm;
		}

		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		end = sched_clock();
		dlog("%s: start task switch at %llu\n", __func__, end);

		if (end - start > MAX_CTXSW_LATENCY)
		msm_trigger_wdog_bite();
		#endif

		/*
		* Since the runqueue lock will be released by the next
		* task (which is an invalid locking op but in the case
		@@ -4579,6 +4623,10 @@ need_resched:
		smp_mb__before_spinlock();
		raw_spin_lock_irq(&rq->lock);

		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		dlog("%s: locked %p at %llu\n", __func__, &rq->lock, sched_clock());
		#endif

		switch_count = &prev->nivcsw;
		if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
		if (unlikely(signal_pending_state(prev->state, prev))) {
		@@ -4623,6 +4671,10 @@ need_resched:
		rq->curr = next;
		++*switch_count;

		#ifdef CONFIG_ARCH_WANTS_CTXSW_LOGGING
		dlog("%s: enter context_switch at %llu\n",
		__func__, sched_clock());
		#endif
		context_switch(rq, prev, next); /* unlocks the rq */
		/*
		* The context switch have flipped the stack from under us
		@@ -8858,6 +8910,7 @@ void __init sched_init(void)
		for_each_possible_cpu(i) {
		struct rq *rq;

		per_cpu(dptr, i) = per_cpu(dbuf, i);
		rq = cpu_rq(i);
		raw_spin_lock_init(&rq->lock);
		rq->nr_running = 0;