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Subject[PATCH 4.9 69/71] ip: process in-order fragments efficiently
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Oskolkov <posk@google.com>

This patch changes the runtime behavior of IP defrag queue:
incoming in-order fragments are added to the end of the current
list/"run" of in-order fragments at the tail.

On some workloads, UDP stream performance is substantially improved:

RX: ./udp_stream -F 10 -T 2 -l 60
TX: ./udp_stream -c -H <host> -F 10 -T 5 -l 60

with this patchset applied on a 10Gbps receiver:

throughput=9524.18
throughput_units=Mbit/s

upstream (net-next):

throughput=4608.93
throughput_units=Mbit/s

Reported-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit a4fd284a1f8fd4b6c59aa59db2185b1e17c5c11c)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/inet_fragment.c | 2
net/ipv4/ip_fragment.c | 110 +++++++++++++++++++++++++++++------------------
2 files changed, 70 insertions(+), 42 deletions(-)

--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -145,7 +145,7 @@ void inet_frag_destroy(struct inet_frag_
fp = xp;
} while (fp);
} else {
- sum_truesize = skb_rbtree_purge(&q->rb_fragments);
+ sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
}
sum = sum_truesize + f->qsize;

--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -125,8 +125,8 @@ static u8 ip4_frag_ecn(u8 tos)

static struct inet_frags ip4_frags;

-static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
- struct net_device *dev);
+static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
+ struct sk_buff *prev_tail, struct net_device *dev);


static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
@@ -217,7 +217,12 @@ static void ip_expire(unsigned long arg)
head = skb_rb_first(&qp->q.rb_fragments);
if (!head)
goto out;
- rb_erase(&head->rbnode, &qp->q.rb_fragments);
+ if (FRAG_CB(head)->next_frag)
+ rb_replace_node(&head->rbnode,
+ &FRAG_CB(head)->next_frag->rbnode,
+ &qp->q.rb_fragments);
+ else
+ rb_erase(&head->rbnode, &qp->q.rb_fragments);
memset(&head->rbnode, 0, sizeof(head->rbnode));
barrier();
}
@@ -318,7 +323,7 @@ static int ip_frag_reinit(struct ipq *qp
return -ETIMEDOUT;
}

- sum_truesize = skb_rbtree_purge(&qp->q.rb_fragments);
+ sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments);
sub_frag_mem_limit(qp->q.net, sum_truesize);

qp->q.flags = 0;
@@ -327,6 +332,7 @@ static int ip_frag_reinit(struct ipq *qp
qp->q.fragments = NULL;
qp->q.rb_fragments = RB_ROOT;
qp->q.fragments_tail = NULL;
+ qp->q.last_run_head = NULL;
qp->iif = 0;
qp->ecn = 0;

@@ -338,7 +344,7 @@ static int ip_frag_queue(struct ipq *qp,
{
struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
struct rb_node **rbn, *parent;
- struct sk_buff *skb1;
+ struct sk_buff *skb1, *prev_tail;
struct net_device *dev;
unsigned int fragsize;
int flags, offset;
@@ -416,38 +422,41 @@ static int ip_frag_queue(struct ipq *qp,
*/

/* Find out where to put this fragment. */
- skb1 = qp->q.fragments_tail;
- if (!skb1) {
- /* This is the first fragment we've received. */
- rb_link_node(&skb->rbnode, NULL, &qp->q.rb_fragments.rb_node);
- qp->q.fragments_tail = skb;
- } else if ((skb1->ip_defrag_offset + skb1->len) < end) {
- /* This is the common/special case: skb goes to the end. */
+ prev_tail = qp->q.fragments_tail;
+ if (!prev_tail)
+ ip4_frag_create_run(&qp->q, skb); /* First fragment. */
+ else if (prev_tail->ip_defrag_offset + prev_tail->len < end) {
+ /* This is the common case: skb goes to the end. */
/* Detect and discard overlaps. */
- if (offset < (skb1->ip_defrag_offset + skb1->len))
+ if (offset < prev_tail->ip_defrag_offset + prev_tail->len)
goto discard_qp;
- /* Insert after skb1. */
- rb_link_node(&skb->rbnode, &skb1->rbnode, &skb1->rbnode.rb_right);
- qp->q.fragments_tail = skb;
+ if (offset == prev_tail->ip_defrag_offset + prev_tail->len)
+ ip4_frag_append_to_last_run(&qp->q, skb);
+ else
+ ip4_frag_create_run(&qp->q, skb);
} else {
- /* Binary search. Note that skb can become the first fragment, but
- * not the last (covered above). */
+ /* Binary search. Note that skb can become the first fragment,
+ * but not the last (covered above).
+ */
rbn = &qp->q.rb_fragments.rb_node;
do {
parent = *rbn;
skb1 = rb_to_skb(parent);
if (end <= skb1->ip_defrag_offset)
rbn = &parent->rb_left;
- else if (offset >= skb1->ip_defrag_offset + skb1->len)
+ else if (offset >= skb1->ip_defrag_offset +
+ FRAG_CB(skb1)->frag_run_len)
rbn = &parent->rb_right;
else /* Found an overlap with skb1. */
goto discard_qp;
} while (*rbn);
/* Here we have parent properly set, and rbn pointing to
- * one of its NULL left/right children. Insert skb. */
+ * one of its NULL left/right children. Insert skb.
+ */
+ ip4_frag_init_run(skb);
rb_link_node(&skb->rbnode, parent, rbn);
+ rb_insert_color(&skb->rbnode, &qp->q.rb_fragments);
}
- rb_insert_color(&skb->rbnode, &qp->q.rb_fragments);

if (dev)
qp->iif = dev->ifindex;
@@ -474,7 +483,7 @@ static int ip_frag_queue(struct ipq *qp,
unsigned long orefdst = skb->_skb_refdst;

skb->_skb_refdst = 0UL;
- err = ip_frag_reasm(qp, skb, dev);
+ err = ip_frag_reasm(qp, skb, prev_tail, dev);
skb->_skb_refdst = orefdst;
return err;
}
@@ -493,7 +502,7 @@ err:

/* Build a new IP datagram from all its fragments. */
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
- struct net_device *dev)
+ struct sk_buff *prev_tail, struct net_device *dev)
{
struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
struct iphdr *iph;
@@ -517,10 +526,16 @@ static int ip_frag_reasm(struct ipq *qp,
fp = skb_clone(skb, GFP_ATOMIC);
if (!fp)
goto out_nomem;
- rb_replace_node(&skb->rbnode, &fp->rbnode, &qp->q.rb_fragments);
+ FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
+ if (RB_EMPTY_NODE(&skb->rbnode))
+ FRAG_CB(prev_tail)->next_frag = fp;
+ else
+ rb_replace_node(&skb->rbnode, &fp->rbnode,
+ &qp->q.rb_fragments);
if (qp->q.fragments_tail == skb)
qp->q.fragments_tail = fp;
skb_morph(skb, head);
+ FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
rb_replace_node(&head->rbnode, &skb->rbnode,
&qp->q.rb_fragments);
consume_skb(head);
@@ -556,7 +571,7 @@ static int ip_frag_reasm(struct ipq *qp,
for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
clone->len = clone->data_len = head->data_len - plen;
- skb->truesize += clone->truesize;
+ head->truesize += clone->truesize;
clone->csum = 0;
clone->ip_summed = head->ip_summed;
add_frag_mem_limit(qp->q.net, clone->truesize);
@@ -569,24 +584,36 @@ static int ip_frag_reasm(struct ipq *qp,
skb_push(head, head->data - skb_network_header(head));

/* Traverse the tree in order, to build frag_list. */
+ fp = FRAG_CB(head)->next_frag;
rbn = rb_next(&head->rbnode);
rb_erase(&head->rbnode, &qp->q.rb_fragments);
- while (rbn) {
- struct rb_node *rbnext = rb_next(rbn);
- fp = rb_to_skb(rbn);
- rb_erase(rbn, &qp->q.rb_fragments);
- rbn = rbnext;
- *nextp = fp;
- nextp = &fp->next;
- fp->prev = NULL;
- memset(&fp->rbnode, 0, sizeof(fp->rbnode));
- head->data_len += fp->len;
- head->len += fp->len;
- if (head->ip_summed != fp->ip_summed)
- head->ip_summed = CHECKSUM_NONE;
- else if (head->ip_summed == CHECKSUM_COMPLETE)
- head->csum = csum_add(head->csum, fp->csum);
- head->truesize += fp->truesize;
+ while (rbn || fp) {
+ /* fp points to the next sk_buff in the current run;
+ * rbn points to the next run.
+ */
+ /* Go through the current run. */
+ while (fp) {
+ *nextp = fp;
+ nextp = &fp->next;
+ fp->prev = NULL;
+ memset(&fp->rbnode, 0, sizeof(fp->rbnode));
+ head->data_len += fp->len;
+ head->len += fp->len;
+ if (head->ip_summed != fp->ip_summed)
+ head->ip_summed = CHECKSUM_NONE;
+ else if (head->ip_summed == CHECKSUM_COMPLETE)
+ head->csum = csum_add(head->csum, fp->csum);
+ head->truesize += fp->truesize;
+ fp = FRAG_CB(fp)->next_frag;
+ }
+ /* Move to the next run. */
+ if (rbn) {
+ struct rb_node *rbnext = rb_next(rbn);
+
+ fp = rb_to_skb(rbn);
+ rb_erase(rbn, &qp->q.rb_fragments);
+ rbn = rbnext;
+ }
}
sub_frag_mem_limit(qp->q.net, head->truesize);

@@ -622,6 +649,7 @@ static int ip_frag_reasm(struct ipq *qp,
qp->q.fragments = NULL;
qp->q.rb_fragments = RB_ROOT;
qp->q.fragments_tail = NULL;
+ qp->q.last_run_head = NULL;
return 0;

out_nomem:

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