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net:Add sysctl_max_skb_frags

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Devices may have limits on the number of fragments in an skb they support.
Current codebase uses a constant as maximum for number of fragments one
skb can hold and use.
When enabling scatter/gather and running traffic with many small messages
the codebase uses the maximum number of fragments and may thereby violate
the max for certain devices.
The patch introduces a global variable as max number of fragments.

Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hans Westgaard Ry 2016-02-03 09:26:57 +01:00 committed by David S. Miller
parent 9cf7490360
commit 5f74f82ea3
4 changed files with 15 additions and 2 deletions
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1
include/linux/skbuff.h
View File

@ -299,6 +299,7 @@ struct sk_buff;
#else
#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)
#endif
extern int sysctl_max_skb_frags;
typedef struct skb_frag_struct skb_frag_t;

2
net/core/skbuff.c
View File

@ -79,6 +79,8 @@
struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;
int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;
EXPORT_SYMBOL(sysctl_max_skb_frags);
/**
* skb_panic - private function for out-of-line support

10
net/core/sysctl_net_core.c
View File

@ -26,6 +26,7 @@ static int zero = 0;
static int one = 1;
static int min_sndbuf = SOCK_MIN_SNDBUF;
static int min_rcvbuf = SOCK_MIN_RCVBUF;
static int max_skb_frags = MAX_SKB_FRAGS;
static int net_msg_warn; /* Unused, but still a sysctl */
@ -392,6 +393,15 @@ static struct ctl_table net_core_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "max_skb_frags",
.data = &sysctl_max_skb_frags,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &one,
.extra2 = &max_skb_frags,
},
{ }
};

4
net/ipv4/tcp.c
View File

@ -940,7 +940,7 @@ new_segment:
i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
if (!can_coalesce && i >= MAX_SKB_FRAGS) {
if (!can_coalesce && i >= sysctl_max_skb_frags) {
tcp_mark_push(tp, skb);
goto new_segment;
}
@ -1213,7 +1213,7 @@ new_segment:
if (!skb_can_coalesce(skb, i, pfrag->page,
pfrag->offset)) {
if (i == MAX_SKB_FRAGS || !sg) {
if (i == sysctl_max_skb_frags || !sg) {
tcp_mark_push(tp, skb);
goto new_segment;
}