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htb: refactor struct htb_sched fields for performance

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htb_sched structures are big, and source of false sharing on SMP.

Every time a packet is queued or dequeue, many cache lines must be
touched because structures are not lay out properly.

By carefully splitting htb_sched in two parts, and define sub structures
to increase data locality, we can improve performance dramatically on
SMP.

New htb_prio structure can also be used in htb_class to increase data
locality.

I got 26 % performance increase on a 24 threads machine, with 200
concurrent netperf in TCP_RR mode, using a HTB hierarchy of 4 classes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-06-15 03:30:10 -07:00 committed by David S. Miller
parent bcefe17cff
commit c9364636dc
1 changed files with 99 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

189
net/sched/sch_htb.c
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@ -76,6 +76,20 @@ enum htb_cmode {
HTB_CAN_SEND /* class can send */
};
struct htb_prio {
union {
struct rb_root row;
struct rb_root feed;
};
struct rb_node *ptr;
/* When class changes from state 1->2 and disconnects from
* parent's feed then we lost ptr value and start from the
* first child again. Here we store classid of the
* last valid ptr (used when ptr is NULL).
*/
u32 last_ptr_id;
};
/* interior & leaf nodes; props specific to leaves are marked L:
* To reduce false sharing, place mostly read fields at beginning,
* and mostly written ones at the end.
@ -112,19 +126,12 @@ struct htb_class {
union {
struct htb_class_leaf {
struct Qdisc *q;
int deficit[TC_HTB_MAXDEPTH];
struct list_head drop_list;
int deficit[TC_HTB_MAXDEPTH];
struct Qdisc *q;
} leaf;
struct htb_class_inner {
struct rb_root feed[TC_HTB_NUMPRIO]; /* feed trees */
struct rb_node *ptr[TC_HTB_NUMPRIO]; /* current class ptr */
/* When class changes from state 1->2 and disconnects from
* parent's feed then we lost ptr value and start from the
* first child again. Here we store classid of the
* last valid ptr (used when ptr is NULL).
*/
u32 last_ptr_id[TC_HTB_NUMPRIO];
struct htb_prio clprio[TC_HTB_NUMPRIO];
} inner;
} un;
s64 pq_key;
@ -135,40 +142,39 @@ struct htb_class {
struct rb_node node[TC_HTB_NUMPRIO]; /* node for self or feed tree */
};
struct htb_level {
struct rb_root wait_pq;
struct htb_prio hprio[TC_HTB_NUMPRIO];
};
struct htb_sched {
struct Qdisc_class_hash clhash;
struct list_head drops[TC_HTB_NUMPRIO];/* active leaves (for drops) */
/* self list - roots of self generating tree */
struct rb_root row[TC_HTB_MAXDEPTH][TC_HTB_NUMPRIO];
int row_mask[TC_HTB_MAXDEPTH];
struct rb_node *ptr[TC_HTB_MAXDEPTH][TC_HTB_NUMPRIO];
u32 last_ptr_id[TC_HTB_MAXDEPTH][TC_HTB_NUMPRIO];
/* self wait list - roots of wait PQs per row */
struct rb_root wait_pq[TC_HTB_MAXDEPTH];
/* time of nearest event per level (row) */
s64 near_ev_cache[TC_HTB_MAXDEPTH];
int defcls; /* class where unclassified flows go to */
int defcls; /* class where unclassified flows go to */
int rate2quantum; /* quant = rate / rate2quantum */
/* filters for qdisc itself */
struct tcf_proto *filter_list;
int rate2quantum; /* quant = rate / rate2quantum */
s64 now; /* cached dequeue time */
struct qdisc_watchdog watchdog;
/* non shaped skbs; let them go directly thru */
struct sk_buff_head direct_queue;
int direct_qlen; /* max qlen of above */
long direct_pkts;
struct tcf_proto *filter_list;
#define HTB_WARN_TOOMANYEVENTS 0x1
unsigned int warned; /* only one warning */
struct work_struct work;
unsigned int warned; /* only one warning */
int direct_qlen;
struct work_struct work;
/* non shaped skbs; let them go directly thru */
struct sk_buff_head direct_queue;
long direct_pkts;
struct qdisc_watchdog watchdog;
s64 now; /* cached dequeue time */
struct list_head drops[TC_HTB_NUMPRIO];/* active leaves (for drops) */
/* time of nearest event per level (row) */
s64 near_ev_cache[TC_HTB_MAXDEPTH];
int row_mask[TC_HTB_MAXDEPTH];
struct htb_level hlevel[TC_HTB_MAXDEPTH];
};
/* find class in global hash table using given handle */
@ -284,7 +290,7 @@ static void htb_add_to_id_tree(struct rb_root *root,
static void htb_add_to_wait_tree(struct htb_sched *q,
struct htb_class *cl, s64 delay)
{
struct rb_node **p = &q->wait_pq[cl->level].rb_node, *parent = NULL;
struct rb_node **p = &q->hlevel[cl->level].wait_pq.rb_node, *parent = NULL;
cl->pq_key = q->now + delay;
if (cl->pq_key == q->now)
@ -304,7 +310,7 @@ static void htb_add_to_wait_tree(struct htb_sched *q,
p = &parent->rb_left;
}
rb_link_node(&cl->pq_node, parent, p);
rb_insert_color(&cl->pq_node, &q->wait_pq[cl->level]);
rb_insert_color(&cl->pq_node, &q->hlevel[cl->level].wait_pq);
}
/**
@ -331,7 +337,7 @@ static inline void htb_add_class_to_row(struct htb_sched *q,
while (mask) {
int prio = ffz(~mask);
mask &= ~(1 << prio);
htb_add_to_id_tree(q->row[cl->level] + prio, cl, prio);
htb_add_to_id_tree(&q->hlevel[cl->level].hprio[prio].row, cl, prio);
}
}
@ -357,16 +363,18 @@ static inline void htb_remove_class_from_row(struct htb_sched *q,
struct htb_class *cl, int mask)
{
int m = 0;
struct htb_level *hlevel = &q->hlevel[cl->level];
while (mask) {
int prio = ffz(~mask);
struct htb_prio *hprio = &hlevel->hprio[prio];
mask &= ~(1 << prio);
if (q->ptr[cl->level][prio] == cl->node + prio)
htb_next_rb_node(q->ptr[cl->level] + prio);
if (hprio->ptr == cl->node + prio)
htb_next_rb_node(&hprio->ptr);
htb_safe_rb_erase(cl->node + prio, q->row[cl->level] + prio);
if (!q->row[cl->level][prio].rb_node)
htb_safe_rb_erase(cl->node + prio, &hprio->row);
if (!hprio->row.rb_node)
m |= 1 << prio;
}
q->row_mask[cl->level] &= ~m;
@ -390,13 +398,13 @@ static void htb_activate_prios(struct htb_sched *q, struct htb_class *cl)
int prio = ffz(~m);
m &= ~(1 << prio);
if (p->un.inner.feed[prio].rb_node)
if (p->un.inner.clprio[prio].feed.rb_node)
/* parent already has its feed in use so that
* reset bit in mask as parent is already ok
*/
mask &= ~(1 << prio);
htb_add_to_id_tree(p->un.inner.feed + prio, cl, prio);
htb_add_to_id_tree(&p->un.inner.clprio[prio].feed, cl, prio);
}
p->prio_activity |= mask;
cl = p;
@ -426,18 +434,19 @@ static void htb_deactivate_prios(struct htb_sched *q, struct htb_class *cl)
int prio = ffz(~m);
m &= ~(1 << prio);
if (p->un.inner.ptr[prio] == cl->node + prio) {
if (p->un.inner.clprio[prio].ptr == cl->node + prio) {
/* we are removing child which is pointed to from
* parent feed - forget the pointer but remember
* classid
*/
p->un.inner.last_ptr_id[prio] = cl->common.classid;
p->un.inner.ptr[prio] = NULL;
p->un.inner.clprio[prio].last_ptr_id = cl->common.classid;
p->un.inner.clprio[prio].ptr = NULL;
}
htb_safe_rb_erase(cl->node + prio, p->un.inner.feed + prio);
htb_safe_rb_erase(cl->node + prio,
&p->un.inner.clprio[prio].feed);
if (!p->un.inner.feed[prio].rb_node)
if (!p->un.inner.clprio[prio].feed.rb_node)
mask |= 1 << prio;
}
@ -652,7 +661,7 @@ static void htb_charge_class(struct htb_sched *q, struct htb_class *cl,
htb_change_class_mode(q, cl, &diff);
if (old_mode != cl->cmode) {
if (old_mode != HTB_CAN_SEND)
htb_safe_rb_erase(&cl->pq_node, q->wait_pq + cl->level);
htb_safe_rb_erase(&cl->pq_node, &q->hlevel[cl->level].wait_pq);
if (cl->cmode != HTB_CAN_SEND)
htb_add_to_wait_tree(q, cl, diff);
}
@ -672,7 +681,7 @@ static void htb_charge_class(struct htb_sched *q, struct htb_class *cl,
* next pending event (0 for no event in pq, q->now for too many events).
* Note: Applied are events whose have cl->pq_key <= q->now.
*/
static s64 htb_do_events(struct htb_sched *q, int level,
static s64 htb_do_events(struct htb_sched *q, const int level,
unsigned long start)
{
/* don't run for longer than 2 jiffies; 2 is used instead of
@ -680,10 +689,12 @@ static s64 htb_do_events(struct htb_sched *q, int level,
* too soon
*/
unsigned long stop_at = start + 2;
struct rb_root *wait_pq = &q->hlevel[level].wait_pq;
while (time_before(jiffies, stop_at)) {
struct htb_class *cl;
s64 diff;
struct rb_node *p = rb_first(&q->wait_pq[level]);
struct rb_node *p = rb_first(wait_pq);
if (!p)
return 0;
@ -692,7 +703,7 @@ static s64 htb_do_events(struct htb_sched *q, int level,
if (cl->pq_key > q->now)
return cl->pq_key;
htb_safe_rb_erase(p, q->wait_pq + level);
htb_safe_rb_erase(p, wait_pq);
diff = min_t(s64, q->now - cl->t_c, cl->mbuffer);
htb_change_class_mode(q, cl, &diff);
if (cl->cmode != HTB_CAN_SEND)
@ -736,8 +747,7 @@ static struct rb_node *htb_id_find_next_upper(int prio, struct rb_node *n,
*
* Find leaf where current feed pointers points to.
*/
static struct htb_class *htb_lookup_leaf(struct rb_root *tree, int prio,
struct rb_node **pptr, u32 * pid)
static struct htb_class *htb_lookup_leaf(struct htb_prio *hprio, const int prio)
{
int i;
struct {
@ -746,10 +756,10 @@ static struct htb_class *htb_lookup_leaf(struct rb_root *tree, int prio,
u32 *pid;
} stk[TC_HTB_MAXDEPTH], *sp = stk;
BUG_ON(!tree->rb_node);
sp->root = tree->rb_node;
sp->pptr = pptr;
sp->pid = pid;
BUG_ON(!hprio->row.rb_node);
sp->root = hprio->row.rb_node;
sp->pptr = &hprio->ptr;
sp->pid = &hprio->last_ptr_id;
for (i = 0; i < 65535; i++) {
if (!*sp->pptr && *sp->pid) {
@ -776,12 +786,15 @@ static struct htb_class *htb_lookup_leaf(struct rb_root *tree, int prio,
}
} else {
struct htb_class *cl;
struct htb_prio *clp;
cl = rb_entry(*sp->pptr, struct htb_class, node[prio]);
if (!cl->level)
return cl;
(++sp)->root = cl->un.inner.feed[prio].rb_node;
sp->pptr = cl->un.inner.ptr + prio;
sp->pid = cl->un.inner.last_ptr_id + prio;
clp = &cl->un.inner.clprio[prio];
(++sp)->root = clp->feed.rb_node;
sp->pptr = &clp->ptr;
sp->pid = &clp->last_ptr_id;
}
}
WARN_ON(1);
@ -791,15 +804,16 @@ static struct htb_class *htb_lookup_leaf(struct rb_root *tree, int prio,
/* dequeues packet at given priority and level; call only if
* you are sure that there is active class at prio/level
*/
static struct sk_buff *htb_dequeue_tree(struct htb_sched *q, int prio,
int level)
static struct sk_buff *htb_dequeue_tree(struct htb_sched *q, const int prio,
const int level)
{
struct sk_buff *skb = NULL;
struct htb_class *cl, *start;
struct htb_level *hlevel = &q->hlevel[level];
struct htb_prio *hprio = &hlevel->hprio[prio];
/* look initial class up in the row */
start = cl = htb_lookup_leaf(q->row[level] + prio, prio,
q->ptr[level] + prio,
q->last_ptr_id[level] + prio);
start = cl = htb_lookup_leaf(hprio, prio);
do {
next:
@ -819,9 +833,7 @@ next:
if ((q->row_mask[level] & (1 << prio)) == 0)
return NULL;
next = htb_lookup_leaf(q->row[level] + prio,
prio, q->ptr[level] + prio,
q->last_ptr_id[level] + prio);
next = htb_lookup_leaf(hprio, prio);
if (cl == start) /* fix start if we just deleted it */
start = next;
@ -834,11 +846,9 @@ next:
break;
qdisc_warn_nonwc("htb", cl->un.leaf.q);
htb_next_rb_node((level ? cl->parent->un.inner.ptr : q->
ptr[0]) + prio);
cl = htb_lookup_leaf(q->row[level] + prio, prio,
q->ptr[level] + prio,
q->last_ptr_id[level] + prio);
htb_next_rb_node(level ? &cl->parent->un.inner.clprio[prio].ptr:
&q->hlevel[0].hprio[prio].ptr);
cl = htb_lookup_leaf(hprio, prio);
} while (cl != start);
@ -847,8 +857,8 @@ next:
cl->un.leaf.deficit[level] -= qdisc_pkt_len(skb);
if (cl->un.leaf.deficit[level] < 0) {
cl->un.leaf.deficit[level] += cl->quantum;
htb_next_rb_node((level ? cl->parent->un.inner.ptr : q->
ptr[0]) + prio);
htb_next_rb_node(level ? &cl->parent->un.inner.clprio[prio].ptr :
&q->hlevel[0].hprio[prio].ptr);
}
/* this used to be after charge_class but this constelation
* gives us slightly better performance
@ -888,15 +898,14 @@ ok:
for (level = 0; level < TC_HTB_MAXDEPTH; level++) {
/* common case optimization - skip event handler quickly */
int m;
s64 event;
s64 event = q->near_ev_cache[level];
if (q->now >= q->near_ev_cache[level]) {
if (q->now >= event) {
event = htb_do_events(q, level, start_at);
if (!event)
event = q->now + NSEC_PER_SEC;
q->near_ev_cache[level] = event;
} else
event = q->near_ev_cache[level];
}
if (next_event > event)
next_event = event;
@ -976,10 +985,8 @@ static void htb_reset(struct Qdisc *sch)
qdisc_watchdog_cancel(&q->watchdog);
__skb_queue_purge(&q->direct_queue);
sch->q.qlen = 0;
memset(q->row, 0, sizeof(q->row));
memset(q->hlevel, 0, sizeof(q->hlevel));
memset(q->row_mask, 0, sizeof(q->row_mask));
memset(q->wait_pq, 0, sizeof(q->wait_pq));
memset(q->ptr, 0, sizeof(q->ptr));
for (i = 0; i < TC_HTB_NUMPRIO; i++)
INIT_LIST_HEAD(q->drops + i);
}
@ -1200,7 +1207,8 @@ static void htb_parent_to_leaf(struct htb_sched *q, struct htb_class *cl,
WARN_ON(cl->level || !cl->un.leaf.q || cl->prio_activity);
if (parent->cmode != HTB_CAN_SEND)
htb_safe_rb_erase(&parent->pq_node, q->wait_pq + parent->level);
htb_safe_rb_erase(&parent->pq_node,
&q->hlevel[parent->level].wait_pq);
parent->level = 0;
memset(&parent->un.inner, 0, sizeof(parent->un.inner));
@ -1289,7 +1297,8 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
htb_deactivate(q, cl);
if (cl->cmode != HTB_CAN_SEND)
htb_safe_rb_erase(&cl->pq_node, q->wait_pq + cl->level);
htb_safe_rb_erase(&cl->pq_node,
&q->hlevel[cl->level].wait_pq);
if (last_child)
htb_parent_to_leaf(q, cl, new_q);
@ -1411,7 +1420,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
/* remove from evt list because of level change */
if (parent->cmode != HTB_CAN_SEND) {
htb_safe_rb_erase(&parent->pq_node, q->wait_pq);
htb_safe_rb_erase(&parent->pq_node, &q->hlevel[0].wait_pq);
parent->cmode = HTB_CAN_SEND;
}
parent->level = (parent->parent ? parent->parent->level