Re: [Tarantool-patches] [PATCH v3 1/3] fiber.top() refactor clock and cpu time calculation

["Sergey Petrenko" <sergepetrenko@tarantool.org>]

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>Вторник, 19 ноября 2019, 1:19 +03:00 от Vladislav Shpilevoy <v.shpilevoy@tarantool.org>:
>
>Hi! Thanks for the fixes!
>
>I suggest you to move all functions related to cpu and clock
>state to fiber.c and make them static there. In order not to
>pollute the global namespace with fiber's private functions.
>
>I did that in a commit above this one. You may squash, or redo,
>whatever:
Hi! Thanks, I squashed.
>
>
>===================================================================
>
>diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
>index 1e08d0ec9..3faa198d3 100644
>--- a/src/lib/core/fiber.c
>+++ b/src/lib/core/fiber.c
>@@ -44,6 +44,112 @@
>
> #if ENABLE_FIBER_TOP
> #include <x86intrin.h> /* __rdtscp() */
>+
>+static inline void
>+clock_stat_add_delta(struct clock_stat *stat, uint64_t clock_delta)
>+{
>+	stat->delta += clock_delta;
>+}
>+
>+/**
>+ * Calculate the exponential moving average for the clock deltas
>+ * per loop iteration. The coeffitient is 1/16.
>+ */
>+static inline uint64_t
>+clock_diff_accumulate(uint64_t acc, uint64_t delta)
>+{
>+	if (acc > 0)
>+		return delta / 16 + 15 * acc / 16;
>+	else
>+		return delta;
>+}
>+
>+static inline void
>+clock_stat_update(struct clock_stat *stat, double nsec_per_clock)
>+{
>+	stat->acc = clock_diff_accumulate(stat->acc, stat->delta);
>+	stat->prev_delta = stat->delta;
>+	stat->cputime += stat->delta * nsec_per_clock;
>+	stat->delta = 0;
>+}
>+
>+static inline void
>+clock_stat_reset(struct clock_stat *stat)
>+{
>+	stat->acc = 0;
>+	stat->delta = 0;
>+	stat->prev_delta = 0;
>+	stat->cputime = 0;
>+}
>+
>+static void
>+cpu_stat_start(struct cpu_stat *stat)
>+{
>+	stat->prev_clock = __rdtscp(&stat->prev_cpu_id);
>+	stat->cpu_miss_count = 0;
>+	/*
>+	 * We want to measure thread cpu time here to calculate
>+	 * each fiber's cpu time, so don't use libev's ev_now() or
>+	 * ev_time() since they use either monotonic or realtime
>+	 * system clocks.
>+	 */
>+	struct timespec ts;
>+	if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0) {
>+		say_debug("clock_gettime(): failed to get this thread's"
>+			  " cpu time.");
>+		return;
>+	}
>+	stat->prev_cputime = (uint64_t) ts.tv_sec * FIBER_TIME_RES + ts.tv_nsec;
>+}
>+
>+static inline void
>+cpu_stat_reset(struct cpu_stat *stat)
>+{
>+	stat->prev_cpu_miss_count = 0;
>+	cpu_stat_start(stat);
>+}
>+
>+static uint64_t
>+cpu_stat_on_csw(struct cpu_stat *stat)
>+{
>+	uint32_t cpu_id;
>+	uint64_t delta, clock = __rdtscp(&cpu_id);
>+
>+	if (cpu_id == stat->prev_cpu_id) {
>+		delta = clock - stat->prev_clock;
>+	} else {
>+		delta = 0;
>+		stat->prev_cpu_id = cpu_id;
>+		stat->cpu_miss_count++;
>+	}
>+	stat->prev_clock = clock;
>+
>+	return delta;
>+}
>+
>+static double
>+cpu_stat_end(struct cpu_stat *stat, struct clock_stat *cord_clock_stat)
>+{
>+	stat->prev_cpu_miss_count = stat->cpu_miss_count;
>+	stat->cpu_miss_count = 0;
>+
>+	struct timespec ts;
>+	uint64_t delta_time;
>+	double nsec_per_clock = 0;
>+	if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0) {
>+		say_debug("clock_gettime(): failed to get this thread's"
>+			  " cpu time.");
>+	} else {
>+		delta_time = (uint64_t) ts.tv_sec * FIBER_TIME_RES +
>+			     ts.tv_nsec;
>+		if (delta_time > stat->prev_cputime && cord_clock_stat->delta > 0) {
>+			delta_time -= stat->prev_cputime;
>+			nsec_per_clock = (double) delta_time / cord()->clock_stat.delta;
>+		}
>+	}
>+	return nsec_per_clock;
>+}
>+
> #endif /* ENABLE_FIBER_TOP */
>
> #include "third_party/valgrind/memcheck.h"
>@@ -88,9 +194,6 @@ static int (*fiber_invoke)(fiber_func f, va_list ap);
>
> #if ENABLE_FIBER_TOP
> static __thread bool fiber_top_enabled = false;
>-
>-uint64_t
>-cpu_stat_on_csw(struct cpu_stat *stat);
> #endif /* ENABLE_FIBER_TOP */
>
> /**
>@@ -1091,112 +1194,6 @@ loop_on_iteration_start(ev_loop *loop, ev_check *watcher, int revents)
> 	cpu_stat_start(&cord()->cpu_stat);
> }
>
>-/**
>- * Calculate the exponential moving average for the clock deltas
>- * per loop iteration. The coeffitient is 1/16.
>- */
>-static inline uint64_t
>-clock_diff_accumulate(uint64_t acc, uint64_t delta)
>-{
>-	if (acc > 0) {
>-		return delta / 16 + 15 * acc / 16;
>-	} else {
>-		return delta;
>-	}
>-}
>-
>-inline void
>-clock_stat_add_delta(struct clock_stat *stat, uint64_t clock_delta)
>-{
>-	stat->delta += clock_delta;
>-}
>-
>-void
>-clock_stat_update(struct clock_stat *stat, double nsec_per_clock)
>-{
>-	stat->acc = clock_diff_accumulate(stat->acc, stat->delta);
>-	stat->prev_delta = stat->delta;
>-	stat->cputime += stat->delta * nsec_per_clock;
>-	stat->delta = 0;
>-}
>-
>-void
>-clock_stat_reset(struct clock_stat *stat)
>-{
>-	stat->acc = 0;
>-	stat->delta = 0;
>-	stat->prev_delta = 0;
>-	stat->cputime = 0;
>-}
>-
>-void
>-cpu_stat_start(struct cpu_stat *stat)
>-{
>-	stat->prev_clock = __rdtscp(&stat->prev_cpu_id);
>-	stat->cpu_miss_count = 0;
>-	/*
>-	 * We want to measure thread cpu time here to calculate
>-	 * each fiber's cpu time, so don't use libev's ev_now() or
>-	 * ev_time() since they use either monotonic or realtime
>-	 * system clocks.
>-	 */
>-	struct timespec ts;
>-	if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0) {
>-		say_debug("clock_gettime(): failed to get this thread's"
>-			  " cpu time.");
>-		return;
>-	}
>-	stat->prev_cputime = (uint64_t) ts.tv_sec * FIBER_TIME_RES + ts.tv_nsec;
>-}
>-
>-void
>-cpu_stat_reset(struct cpu_stat *stat)
>-{
>-	stat->prev_cpu_miss_count = 0;
>-	cpu_stat_start(stat);
>-}
>-
>-uint64_t
>-cpu_stat_on_csw(struct cpu_stat *stat)
>-{
>-	uint32_t cpu_id;
>-	uint64_t delta = 0;
>-	uint64_t clock = __rdtscp(&cpu_id);
>-
>-	if (cpu_id == stat->prev_cpu_id) {
>-		delta = clock - stat->prev_clock;
>-	} else {
>-		stat->prev_cpu_id = cpu_id;
>-		stat->cpu_miss_count++;
>-	}
>-	stat->prev_clock = clock;
>-
>-	return delta;
>-}
>-
>-double
>-cpu_stat_end(struct cpu_stat *stat, struct clock_stat *cord_clock_stat)
>-{
>-	stat->prev_cpu_miss_count = stat->cpu_miss_count;
>-	stat->cpu_miss_count = 0;
>-
>-	struct timespec ts;
>-	uint64_t delta_time;
>-	double nsec_per_clock = 0;
>-	if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0) {
>-		say_debug("clock_gettime(): failed to get this thread's"
>-			  " cpu time.");
>-	} else {
>-		delta_time = (uint64_t) ts.tv_sec * FIBER_TIME_RES +
>-			     ts.tv_nsec;
>-		if (delta_time > stat->prev_cputime && cord_clock_stat->delta > 0) {
>-			delta_time -= stat->prev_cputime;
>-			nsec_per_clock = (double) delta_time / cord()->clock_stat.delta;
>-		}
>-	}
>-	return nsec_per_clock;
>-}
>-
> static void
> loop_on_iteration_end(ev_loop *loop, ev_prepare *watcher, int revents)
> {
>diff --git a/src/lib/core/fiber.h b/src/lib/core/fiber.h
>index 06ce28bb1..c5b975513 100644
>--- a/src/lib/core/fiber.h
>+++ b/src/lib/core/fiber.h
>@@ -91,15 +91,6 @@ struct clock_stat {
> 	uint64_t cputime;
> };
>
>-void
>-clock_stat_add_delta(struct clock_stat *stat, uint64_t clock_delta);
>-
>-void
>-clock_stat_update(struct clock_stat *stat, double nsec_per_clock);
>-
>-void
>-clock_stat_reset(struct clock_stat *stat);
>-
> /**
>  * A struct encapsulating all knowledge this cord has about cpu
>  * clocks and their state.
>@@ -119,18 +110,6 @@ struct cpu_stat {
> 	uint32_t prev_cpu_miss_count;
> };
>
>-void
>-cpu_stat_start(struct cpu_stat *stat);
>-
>-void
>-cpu_stat_reset(struct cpu_stat *stat);
>-
>-uint64_t
>-cpu_stat_on_csw(struct cpu_stat *stat);
>-
>-double
>-cpu_stat_end(struct cpu_stat *stat, struct clock_stat *cord_clock_stat);
>-
> #endif /* ENABLE_FIBER_TOP */
>
> enum { FIBER_NAME_MAX = 32 };


-- 
Sergey Petrenko

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