Hi! Thank you for your answer!
Fixed codestyle and answered your question inline.

--
Serge Petrenko
sergepetrenko@tarantool.org <mailto:sergepetrenko@tarantool.org>

> 15 нояб. 2019 г., в 19:11, Alexander Turenko <alexander.turenko@tarantool.org> написал(а):
> 
> I have no any knowledge around fiber.top(), just asked a question
> because of curiosity.
> 
> WBR, Alexander Turenko.
> 
> On Fri, Nov 15, 2019 at 05:58:58PM +0300, Serge Petrenko wrote:
>> We didn't refresh last remembered clock on fiber.top_enable()
>> This means that the fiber issuing fiber.top_enable() would get a huge
>> chunk of cpu time on its first yield. Fix this.
>> Also reset clock_delta and cpu_miss_count.
>> 
>> If fiber.top() is issued on the same ev loop iteration as
>> fiber.top_enable(), clock_delta_last is 0 for both cord and all the
>> fibers, so report "instant" and "average" stats per last iteration as 0
>> instead of NaN.
>> 
>> Follow-up #2694
>> ---
>> src/lib/core/fiber.c | 21 +++++++++++++++++++++
>> src/lua/fiber.c      | 12 ++++++++++--
>> 2 files changed, 31 insertions(+), 2 deletions(-)
>> 
>> diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
>> index aebaba7f0..258c094f5 100644
>> --- a/src/lib/core/fiber.c
>> +++ b/src/lib/core/fiber.c
>> @@ -1203,9 +1203,30 @@ fiber_top_enable()
>> 		ev_check_start(cord()->loop, &cord()->check_event);
>> 		fiber_top_enabled = true;
>> 
>> +		/*
>> +		 * Reset cord and fiber clock stats in order to
>> +		 * count from zero even on reenable.
>> +		 */
>> 		cord()->clock_acc = 0;
>> 		cord()->cpu_miss_count_last = 0;
>> 		cord()->clock_delta_last = 0;
>> +		cord()->clock_delta = 0;
>> +
>> +		struct fiber * fiber;
> 
> Code style: struct fiber *fiber;

Fixed

> 
>> +		rlist_foreach_entry(fiber, &cord()->alive, link) {
>> +			fiber->clock_acc = 0;
>> +			fiber->clock_delta_last = 0;
>> +			fiber->clock_delta = 0;
>> +			fiber->cputime = 0;
>> +		}
>> +
>> +		cord()->sched.clock_acc = 0;
>> +		cord()->sched.clock_delta_last = 0;
>> +		cord()->sched.clock_delta = 0;
>> +		cord()->sched.cputime = 0;
>> +
>> +		cord()->clock_last = __rdtscp(&cord()->cpu_id_last);
>> +		cord()->cpu_miss_count = 0;
> 
> Should not we doing such clean up in fiber_top_disable() rather then
> here?

It doesn’t matter IMO. Well, yes, you don’t need a cleanup when you call
fiber.top_enable() for the first time, but, other than that, I see no difference.

> 
>> 		struct timespec ts;
>> 		if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0) {
>> 			say_debug("clock_gettime(): failed to get this"
>> diff --git a/src/lua/fiber.c b/src/lua/fiber.c
>> index 8b3b22e55..647505643 100644
>> --- a/src/lua/fiber.c
>> +++ b/src/lua/fiber.c
>> @@ -335,11 +335,19 @@ lbox_fiber_top_entry(struct fiber *f, void *cb_ctx)
>> 	lua_newtable(L);
>> 
>> 	lua_pushliteral(L, "average");
>> -	lua_pushnumber(L, f->clock_acc / (double)cord()->clock_acc * 100);
>> +	if (cord()->clock_acc)
>> +		lua_pushnumber(L, f->clock_acc / (double)cord()->clock_acc * 100);
>> +	else
>> +		lua_pushnumber(L, 0);
>> 	lua_settable(L, -3);
>> +
>> 	lua_pushliteral(L, "instant");
>> -	lua_pushnumber(L, f->clock_delta_last / (double)cord()->clock_delta_last * 100);
>> +	if (cord()->clock_delta_last)
>> +		lua_pushnumber(L, f->clock_delta_last / (double)cord()->clock_delta_last * 100);
>> +	else
>> +		lua_pushnumber(L, 0);
>> 	lua_settable(L, -3);
> 
> Code style: lines over 80 chars.

Fixed

> 
>> +
>> 	lua_pushliteral(L, "time");
>> 	lua_pushnumber(L, f->cputime / (double) FIBER_TIME_RES);
>> 	lua_settable(L, -3);
>> -- 
>> 2.21.0 (Apple Git-122)


diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
index 258c094f5..c6aab18b2 100644
--- a/src/lib/core/fiber.c
+++ b/src/lib/core/fiber.c
@@ -1212,7 +1212,7 @@ fiber_top_enable()
                cord()->clock_delta_last = 0;
                cord()->clock_delta = 0;
 
-               struct fiber * fiber;
+               struct fiber *fiber;
                rlist_foreach_entry(fiber, &cord()->alive, link) {
                        fiber->clock_acc = 0;
                        fiber->clock_delta_last = 0;
diff --git a/src/lua/fiber.c b/src/lua/fiber.c
index 647505643..9268b0a19 100644
--- a/src/lua/fiber.c
+++ b/src/lua/fiber.c
@@ -335,17 +335,21 @@ lbox_fiber_top_entry(struct fiber *f, void *cb_ctx)
        lua_newtable(L);
 
        lua_pushliteral(L, "average");
-       if (cord()->clock_acc)
-               lua_pushnumber(L, f->clock_acc / (double)cord()->clock_acc * 100);
-       else
+       if (cord()->clock_acc) {
+               lua_pushnumber(L, f->clock_acc /
+                                 (double)cord()->clock_acc * 100);
+       } else {
                lua_pushnumber(L, 0);
+       }
        lua_settable(L, -3);
 
        lua_pushliteral(L, "instant");
-       if (cord()->clock_delta_last)
-               lua_pushnumber(L, f->clock_delta_last / (double)cord()->clock_delta_last * 100);
-       else
+       if (cord()->clock_delta_last) {
+               lua_pushnumber(L, f->clock_delta_last /
+                                 (double)cord()->clock_delta_last * 100);
+       } else {
                lua_pushnumber(L, 0);
+       }
        lua_settable(L, -3);
 
        lua_pushliteral(L, "time");