diff mbox series

[v2,net-next,1/3] netem: convert to qdisc_watchdog_schedule_ns

Message ID 1510175399-7404-2-git-send-email-dave.taht@gmail.com
State Superseded, archived
Delegated to: David Miller
Headers show
Series netem: add nsec scheduling and slot feature | expand

Commit Message

Dave Taht Nov. 8, 2017, 9:09 p.m. UTC 
Upgrade the internal netem scheduler to use nanoseconds rather than
ticks throughout.

Convert to and from the std "ticks" userspace api automatically,
while allowing for finer grained scheduling to take place.

Signed-off-by: Dave Taht <dave.taht@gmail.com>
---
 net/sched/sch_netem.c | 56 +++++++++++++++++++++++++--------------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

Comments

Eric Dumazet Nov. 8, 2017, 10:20 p.m. UTC | #1 
On Wed, 2017-11-08 at 13:09 -0800, Dave Taht wrote:
> Upgrade the internal netem scheduler to use nanoseconds rather than
> ticks throughout.
> 
...

> -static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sched_data *q)
> +static s64 packet_len_2_sched_time(unsigned int len,
> +				   struct netem_sched_data *q)
>  {
> -	u64 ticks;
> -
> +	s64 offset;
>  	len += q->packet_overhead;
>  
>  	if (q->cell_size) {
> @@ -345,11 +345,9 @@ static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sche
>  			cells++;
>  		len = cells * (q->cell_size + q->cell_overhead);
>  	}
> -
> -	ticks = (u64)len * NSEC_PER_SEC;
> -
> -	do_div(ticks, q->rate);
> -	return PSCHED_NS2TICKS(ticks);
> +	offset = (s64)len * NSEC_PER_SEC;
> +	do_div(offset, q->rate);
> +	return offset;
>  }

do_div() first argument being u64, I do not see why you chose 
's64 offset'

packet_len_2_sched_time() should return u64, because I do not see how we
could return a negative value, since a packet length is positive.
kernel test robot Nov. 11, 2017, 12:08 p.m. UTC | #2 
Hi Dave,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/Dave-Taht/netem-convert-to-qdisc_watchdog_schedule_ns/20171111-184934
config: xtensa-allyesconfig (attached as .config)
compiler: xtensa-linux-gcc (GCC) 4.9.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=xtensa 

All warnings (new ones prefixed by >>):

   In file included from ./arch/xtensa/include/generated/asm/div64.h:1:0,
                    from include/linux/kernel.h:173,
                    from include/asm-generic/bug.h:16,
                    from ./arch/xtensa/include/generated/asm/bug.h:1,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from net/sched/sch_netem.c:16:
   net/sched/sch_netem.c: In function 'packet_len_2_sched_time':
   include/asm-generic/div64.h:208:28: warning: comparison of distinct pointer types lacks a cast
     (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                               ^
>> net/sched/sch_netem.c:349:2: note: in expansion of macro 'do_div'
     do_div(offset, q->rate);
     ^

vim +/do_div +349 net/sched/sch_netem.c

   334	
   335	static s64 packet_len_2_sched_time(unsigned int len,
   336					   struct netem_sched_data *q)
   337	{
   338		s64 offset;
   339		len += q->packet_overhead;
   340	
   341		if (q->cell_size) {
   342			u32 cells = reciprocal_divide(len, q->cell_size_reciprocal);
   343	
   344			if (len > cells * q->cell_size)	/* extra cell needed for remainder */
   345				cells++;
   346			len = cells * (q->cell_size + q->cell_overhead);
   347		}
   348		offset = (s64)len * NSEC_PER_SEC;
 > 349		do_div(offset, q->rate);
   350		return offset;
   351	}
   352	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
kernel test robot Nov. 11, 2017, 12:28 p.m. UTC | #3 
Hi Dave,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net-next/master]

url:    https://github.com/0day-ci/linux/commits/Dave-Taht/netem-convert-to-qdisc_watchdog_schedule_ns/20171111-184934
config: i386-randconfig-i1-201745 (attached as .config)
compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   net/sched/sch_netem.o: In function `netem_enqueue':
>> net/sched/sch_netem.c:323: undefined reference to `__moddi3'

vim +323 net/sched/sch_netem.c

661b7972 stephen hemminger 2011-02-23  302  
661b7972 stephen hemminger 2011-02-23  303  
^1da177e Linus Torvalds    2005-04-16  304  /* tabledist - return a pseudo-randomly distributed value with mean mu and
^1da177e Linus Torvalds    2005-04-16  305   * std deviation sigma.  Uses table lookup to approximate the desired
^1da177e Linus Torvalds    2005-04-16  306   * distribution, and a uniformly-distributed pseudo-random source.
^1da177e Linus Torvalds    2005-04-16  307   */
9d0cec66 Dave Taht         2017-11-08  308  static s64 tabledist(s64 mu, s64 sigma,
b407621c Stephen Hemminger 2007-03-22  309  		     struct crndstate *state,
b407621c Stephen Hemminger 2007-03-22  310  			 const struct disttable *dist)
^1da177e Linus Torvalds    2005-04-16  311  {
9d0cec66 Dave Taht         2017-11-08  312  	s64 x;
b407621c Stephen Hemminger 2007-03-22  313  	long t;
b407621c Stephen Hemminger 2007-03-22  314  	u32 rnd;
^1da177e Linus Torvalds    2005-04-16  315  
^1da177e Linus Torvalds    2005-04-16  316  	if (sigma == 0)
^1da177e Linus Torvalds    2005-04-16  317  		return mu;
^1da177e Linus Torvalds    2005-04-16  318  
^1da177e Linus Torvalds    2005-04-16  319  	rnd = get_crandom(state);
^1da177e Linus Torvalds    2005-04-16  320  
^1da177e Linus Torvalds    2005-04-16  321  	/* default uniform distribution */
^1da177e Linus Torvalds    2005-04-16  322  	if (dist == NULL)
^1da177e Linus Torvalds    2005-04-16 @323  		return (rnd % (2*sigma)) - sigma + mu;
^1da177e Linus Torvalds    2005-04-16  324  
^1da177e Linus Torvalds    2005-04-16  325  	t = dist->table[rnd % dist->size];
^1da177e Linus Torvalds    2005-04-16  326  	x = (sigma % NETEM_DIST_SCALE) * t;
^1da177e Linus Torvalds    2005-04-16  327  	if (x >= 0)
^1da177e Linus Torvalds    2005-04-16  328  		x += NETEM_DIST_SCALE/2;
^1da177e Linus Torvalds    2005-04-16  329  	else
^1da177e Linus Torvalds    2005-04-16  330  		x -= NETEM_DIST_SCALE/2;
^1da177e Linus Torvalds    2005-04-16  331  
^1da177e Linus Torvalds    2005-04-16  332  	return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
^1da177e Linus Torvalds    2005-04-16  333  }
^1da177e Linus Torvalds    2005-04-16  334  

:::::: The code at line 323 was first introduced by commit
:::::: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Linux-2.6.12-rc2

:::::: TO: Linus Torvalds <torvalds@ppc970.osdl.org>
:::::: CC: Linus Torvalds <torvalds@ppc970.osdl.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
diff mbox series

Patch

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index db0228a..5559ad1 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -77,8 +77,8 @@  struct netem_sched_data {
 
 	struct qdisc_watchdog watchdog;
 
-	psched_tdiff_t latency;
-	psched_tdiff_t jitter;
+	s64 latency;
+	s64 jitter;
 
 	u32 loss;
 	u32 ecn;
@@ -145,7 +145,7 @@  struct netem_sched_data {
  * we save skb->tstamp value in skb->cb[] before destroying it.
  */
 struct netem_skb_cb {
-	psched_time_t	time_to_send;
+	u64	        time_to_send;
 };
 
 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
@@ -305,11 +305,11 @@  static bool loss_event(struct netem_sched_data *q)
  * std deviation sigma.  Uses table lookup to approximate the desired
  * distribution, and a uniformly-distributed pseudo-random source.
  */
-static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
-				struct crndstate *state,
-				const struct disttable *dist)
+static s64 tabledist(s64 mu, s64 sigma,
+		     struct crndstate *state,
+			 const struct disttable *dist)
 {
-	psched_tdiff_t x;
+	s64 x;
 	long t;
 	u32 rnd;
 
@@ -332,10 +332,10 @@  static psched_tdiff_t tabledist(psched_tdiff_t mu, psched_tdiff_t sigma,
 	return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
 }
 
-static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sched_data *q)
+static s64 packet_len_2_sched_time(unsigned int len,
+				   struct netem_sched_data *q)
 {
-	u64 ticks;
-
+	s64 offset;
 	len += q->packet_overhead;
 
 	if (q->cell_size) {
@@ -345,11 +345,9 @@  static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sche
 			cells++;
 		len = cells * (q->cell_size + q->cell_overhead);
 	}
-
-	ticks = (u64)len * NSEC_PER_SEC;
-
-	do_div(ticks, q->rate);
-	return PSCHED_NS2TICKS(ticks);
+	offset = (s64)len * NSEC_PER_SEC;
+	do_div(offset, q->rate);
+	return offset;
 }
 
 static void tfifo_reset(struct Qdisc *sch)
@@ -369,7 +367,7 @@  static void tfifo_reset(struct Qdisc *sch)
 static void tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 {
 	struct netem_sched_data *q = qdisc_priv(sch);
-	psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
+	u64 tnext = netem_skb_cb(nskb)->time_to_send;
 	struct rb_node **p = &q->t_root.rb_node, *parent = NULL;
 
 	while (*p) {
@@ -515,13 +513,13 @@  static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	if (q->gap == 0 ||		/* not doing reordering */
 	    q->counter < q->gap - 1 ||	/* inside last reordering gap */
 	    q->reorder < get_crandom(&q->reorder_cor)) {
-		psched_time_t now;
-		psched_tdiff_t delay;
+		u64 now;
+		s64 delay;
 
 		delay = tabledist(q->latency, q->jitter,
 				  &q->delay_cor, q->delay_dist);
 
-		now = psched_get_time();
+		now = ktime_get_ns();
 
 		if (q->rate) {
 			struct netem_skb_cb *last = NULL;
@@ -547,7 +545,7 @@  static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 				 * from delay.
 				 */
 				delay -= last->time_to_send - now;
-				delay = max_t(psched_tdiff_t, 0, delay);
+				delay = max_t(s64, 0, delay);
 				now = last->time_to_send;
 			}
 
@@ -562,7 +560,7 @@  static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		 * Do re-ordering by putting one out of N packets at the front
 		 * of the queue.
 		 */
-		cb->time_to_send = psched_get_time();
+		cb->time_to_send = ktime_get_ns();
 		q->counter = 0;
 
 		netem_enqueue_skb_head(&sch->q, skb);
@@ -609,13 +607,13 @@  static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 	}
 	p = rb_first(&q->t_root);
 	if (p) {
-		psched_time_t time_to_send;
+		u64 time_to_send;
 
 		skb = rb_to_skb(p);
 
 		/* if more time remaining? */
 		time_to_send = netem_skb_cb(skb)->time_to_send;
-		if (time_to_send <= psched_get_time()) {
+		if (time_to_send <= ktime_get_ns()) {
 			rb_erase(p, &q->t_root);
 
 			sch->q.qlen--;
@@ -659,7 +657,7 @@  static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 			if (skb)
 				goto deliver;
 		}
-		qdisc_watchdog_schedule(&q->watchdog, time_to_send);
+		qdisc_watchdog_schedule_ns(&q->watchdog, time_to_send);
 	}
 
 	if (q->qdisc) {
@@ -888,8 +886,8 @@  static int netem_change(struct Qdisc *sch, struct nlattr *opt)
 
 	sch->limit = qopt->limit;
 
-	q->latency = qopt->latency;
-	q->jitter = qopt->jitter;
+	q->latency = PSCHED_TICKS2NS(qopt->latency);
+	q->jitter = PSCHED_TICKS2NS(qopt->jitter);
 	q->limit = qopt->limit;
 	q->gap = qopt->gap;
 	q->counter = 0;
@@ -1011,8 +1009,10 @@  static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct tc_netem_corrupt corrupt;
 	struct tc_netem_rate rate;
 
-	qopt.latency = q->latency;
-	qopt.jitter = q->jitter;
+	qopt.latency = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->latency),
+			     UINT_MAX);
+	qopt.jitter = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->jitter),
+			    UINT_MAX);
 	qopt.limit = q->limit;
 	qopt.loss = q->loss;
 	qopt.gap = q->gap;