Re: UDP sockets oddities

On 08/26/2017 11:56 AM, Florian Fainelli wrote:

On 08/26/2017 05:47 AM, Eric Dumazet wrote:

quoted

On Fri, 2017-08-25 at 21:19 -0700, David Miller wrote:

quoted

Agreed, but the ARP resolution queue really needs to scale it's backlog
to the physical technology it is attached to.

Yes, last time (in 2011) we increased the old limit of 3 packets :/

We probably should match sysctl_wmem_max so that a single socket
provider would hit its sk_sndbuf limit

Eric, do you want to post this as a formal patch? I don't think I
understand these tunables enough to provide a good commit message
anyways. Thanks!

Before:
/proc/sys/net/ipv4/neigh/eth0/unres_qlen:34
/proc/sys/net/ipv4/neigh/eth0/unres_qlen_bytes:65536
/proc/sys/net/ipv4/neigh/gphy/unres_qlen:34
/proc/sys/net/ipv4/neigh/gphy/unres_qlen_bytes:65536

After:
/proc/sys/net/ipv4/neigh/eth0/unres_qlen:106
/proc/sys/net/ipv4/neigh/eth0/unres_qlen_bytes:229376
/proc/sys/net/ipv4/neigh/gphy/unres_qlen:106
/proc/sys/net/ipv4/neigh/gphy/unres_qlen_bytes:229376

and this does help a lot with the test case reported over an hour, only
2 packets lost:

# perf record -a -g -e skb:kfree_skb iperf -c 192.168.1.23 -b 900M -t
3600 -u
------------------------------------------------------------
Client connecting to 192.168.1.23, UDP port 5001
Sending 1470 byte datagrams, IPG target: 13.07 us (kalman adjust)
UDP buffer size:  224 KByte (default)
------------------------------------------------------------
[  4] local 192.168.1.66 port 48209 connected with 192.168.1.23 port 5001
write failed: Invalid argument
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-404.9 sec  4.51 GBytes  95.7 Mbits/sec
[  4] Sent 3294727 datagrams
[  4] Server Report:
[  4]  0.0-405.1 sec  4.51 GBytes  95.6 Mbits/sec  14.979 ms
2/3294728 (6.1e-05%)

Thanks Eric!

quoted

Something like :

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 6b0bc0f715346a097a6df46e2ba2771359abcd23..7777dceb78107c0019fb39d5b69be1959005b78e 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt

@@ -109,7 +109,8 @@ neigh/default/unres_qlen_bytes - INTEGER
 	queued for each	unresolved address by other network layers.
 	(added in linux 3.3)
 	Setting negative value is meaningless and will return error.
-	Default: 65536 Bytes(64KB)
+	Default: SK_WMEM_MAX, enough to store 256 packets of medium size
+		 (less than 256 bytes per packet)
 
 neigh/default/unres_qlen - INTEGER
 	The maximum number of packets which may be queued for each

diff --git a/include/net/sock.h b/include/net/sock.h
index 1c2912d433e81b10f3fdc87bcfcbb091570edc03..03a362568357acc7278a318423dd3873103f90ca 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h

@@ -2368,6 +2368,16 @@ bool sk_net_capable(const struct sock *sk, int cap);
 
 void sk_get_meminfo(const struct sock *sk, u32 *meminfo);
 
+/* Take into consideration the size of the struct sk_buff overhead in the
+ * determination of these values, since that is non-constant across
+ * platforms.  This makes socket queueing behavior and performance
+ * not depend upon such differences.
+ */
+#define _SK_MEM_PACKETS		256
+#define _SK_MEM_OVERHEAD	SKB_TRUESIZE(256)
+#define SK_WMEM_MAX		(_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
+#define SK_RMEM_MAX		(_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
+
 extern __u32 sysctl_wmem_max;
 extern __u32 sysctl_rmem_max;
 

diff --git a/net/core/sock.c b/net/core/sock.c
index dfdd14cac775e9bfcee0085ee32ffcd0ab28b67b..9b7b6bbb2a23e7652a1f34a305f29d49de00bc8c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c

@@ -307,16 +307,6 @@ static struct lock_class_key af_wlock_keys[AF_MAX];
 static struct lock_class_key af_elock_keys[AF_MAX];
 static struct lock_class_key af_kern_callback_keys[AF_MAX];
 
-/* Take into consideration the size of the struct sk_buff overhead in the
- * determination of these values, since that is non-constant across
- * platforms.  This makes socket queueing behavior and performance
- * not depend upon such differences.
- */
-#define _SK_MEM_PACKETS		256
-#define _SK_MEM_OVERHEAD	SKB_TRUESIZE(256)
-#define SK_WMEM_MAX		(_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
-#define SK_RMEM_MAX		(_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
-
 /* Run time adjustable parameters. */
 __u32 sysctl_wmem_max __read_mostly = SK_WMEM_MAX;
 EXPORT_SYMBOL(sysctl_wmem_max);

diff --git a/net/decnet/dn_neigh.c b/net/decnet/dn_neigh.c
index 21dedf6fd0f76dec22b2b3685beb89cfefea7ded..22bf0b95d6edc3c27ef3a99d27cb70a1551e3e0e 100644
--- a/net/decnet/dn_neigh.c
+++ b/net/decnet/dn_neigh.c

@@ -94,7 +94,7 @@ struct neigh_table dn_neigh_table = {
 			[NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
 			[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
 			[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
-			[NEIGH_VAR_QUEUE_LEN_BYTES] = 64*1024,
+			[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
 			[NEIGH_VAR_PROXY_QLEN] = 0,
 			[NEIGH_VAR_ANYCAST_DELAY] = 0,
 			[NEIGH_VAR_PROXY_DELAY] = 0,

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 8b52179ddc6e54eabf6d3c2ed0132083228680bb..7c45b8896709815c5dde5972fd57cb5c3bcb2648 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c

@@ -171,7 +171,7 @@ struct neigh_table arp_tbl = {
 			[NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
 			[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
 			[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
-			[NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
+			[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
 			[NEIGH_VAR_PROXY_QLEN] = 64,
 			[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
 			[NEIGH_VAR_PROXY_DELAY]	= (8 * HZ) / 10,

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 5e338eb89509b1df6ebd060f8bd19fcb4b86fe05..266a530414d7be4f1e7be922e465bbab46f7cbac 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c

@@ -127,7 +127,7 @@ struct neigh_table nd_tbl = {
 			[NEIGH_VAR_BASE_REACHABLE_TIME] = ND_REACHABLE_TIME,
 			[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
 			[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
-			[NEIGH_VAR_QUEUE_LEN_BYTES] = 64 * 1024,
+			[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
 			[NEIGH_VAR_PROXY_QLEN] = 64,
 			[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
 			[NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,

-- 
Florian