[PATCH] rearrange frto field to save space.

[PATCH] rearrange frto field to save space.

[Stephen Hemminger]

Since the frto_counter field only goes from 0 to 4, it can be moved
into a unused byte size hole to save space.

diff -Nru a/include/linux/tcp.h b/include/linux/tcp.h
--- a/include/linux/tcp.h	Wed Apr 21 10:39:07 2004
+++ b/include/linux/tcp.h	Wed Apr 21 10:39:07 2004
@@ -255,6 +255,10 @@
 	__u8	retransmits;	/* Number of unrecovered RTO timeouts.	*/
 
 	__u8	reordering;	/* Packet reordering metric.		*/
+	__u8	frto_counter;	/* Number of new acks after RTO */
+	__u32	frto_highmark;	/* snd_nxt when RTO occurred */
+
+	__u8	unused_pad;
 	__u8	queue_shrunk;	/* Write queue has been shrunk recently.*/
 	__u8	defer_accept;	/* User waits for some data after accept() */
 
@@ -369,9 +373,6 @@
 	unsigned int		keepalive_time;	  /* time before keep alive takes place */
 	unsigned int		keepalive_intvl;  /* time interval between keep alive probes */
 	int			linger2;
-
-	int                     frto_counter; /* Number of new acks after RTO */
-	__u32                   frto_highmark; /* snd_nxt when RTO occurred */
 
 	unsigned long last_synq_overflow; 
 

[PATCH] add sysctl to turn off caching metrics

[Stephen Hemminger]

When running benchmarks and other experiments, it is often useful
not to save the route metrics (cwnd, rtt) from each connection.
Here is a simple way to do it with sysctl.  Not a new idea, it is part
of the web100 stuff as well.

Patch against 2.6.6-rc2

diff -Nru a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h	Wed Apr 21 10:39:28 2004
+++ b/include/linux/sysctl.h	Wed Apr 21 10:39:28 2004
@@ -326,6 +326,7 @@
 	NET_IPV4_IPFRAG_SECRET_INTERVAL=94,
 	NET_TCP_WESTWOOD=95,
 	NET_IPV4_IGMP_MAX_MSF=96,
+	NET_TCP_NO_METRICS_SAVE=97,
 };
 
 enum {
diff -Nru a/include/net/tcp.h b/include/net/tcp.h
--- a/include/net/tcp.h	Wed Apr 21 10:39:28 2004
+++ b/include/net/tcp.h	Wed Apr 21 10:39:28 2004
@@ -583,6 +583,7 @@
 extern int sysctl_tcp_frto;
 extern int sysctl_tcp_low_latency;
 extern int sysctl_tcp_westwood;
+extern int sysctl_tcp_nometrics_save;
 
 extern atomic_t tcp_memory_allocated;
 extern atomic_t tcp_sockets_allocated;
diff -Nru a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
--- a/net/ipv4/sysctl_net_ipv4.c	Wed Apr 21 10:39:28 2004
+++ b/net/ipv4/sysctl_net_ipv4.c	Wed Apr 21 10:39:28 2004
@@ -594,6 +594,14 @@
 		.strategy	= &sysctl_jiffies
 	},
 	{
+		.ctl_name	= NET_TCP_NO_METRICS_SAVE,
+		.procname	= "tcp_no_metrics_save",
+		.data		= &sysctl_tcp_nometrics_save,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
 		.ctl_name	= NET_TCP_WESTWOOD, 
 		.procname	= "tcp_westwood",
 		.data		= &sysctl_tcp_westwood,
@@ -601,6 +609,7 @@
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+
 	{ .ctl_name = 0 }
 };
 
diff -Nru a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
--- a/net/ipv4/tcp_input.c	Wed Apr 21 10:39:28 2004
+++ b/net/ipv4/tcp_input.c	Wed Apr 21 10:39:28 2004
@@ -87,6 +87,7 @@
 int sysctl_tcp_max_orphans = NR_FILE;
 int sysctl_tcp_frto;
 int sysctl_tcp_westwood;
+int sysctl_tcp_nometrics_save;
 
 #define FLAG_DATA		0x01 /* Incoming frame contained data.		*/
 #define FLAG_WIN_UPDATE		0x02 /* Incoming ACK was a window update.	*/
@@ -517,6 +518,9 @@
 {
 	struct tcp_opt *tp = tcp_sk(sk);
 	struct dst_entry *dst = __sk_dst_get(sk);
+
+	if (sysctl_tcp_nometrics_save)
+		return;
 
 	dst_confirm(dst);
 

Re: [PATCH] rearrange frto field to save space.

[David S. Miller]

On Wed, 21 Apr 2004 11:10:32 -0700
Stephen Hemminger <shemminger@osdl.org> wrote:

> Since the frto_counter field only goes from 0 to 4, it can be moved
> into a unused byte size hole to save space.

Ok. Applied.

Re: [PATCH] add sysctl to turn off caching metrics

[David S. Miller]

On Wed, 21 Apr 2004 11:10:46 -0700
Stephen Hemminger <shemminger@osdl.org> wrote:

> When running benchmarks and other experiments, it is often useful
> not to save the route metrics (cwnd, rtt) from each connection.
> Here is a simple way to do it with sysctl.  Not a new idea, it is part
> of the web100 stuff as well.

This is fine.

Re: [PATCH] rearrange frto field to save space.

[Joe Perches]

On Wed, 2004-04-21 at 11:10, Stephen Hemminger wrote:
> +	__u8	unused_pad;

There's no real reason that I can see to have padding here.

Re: [PATCH] rearrange frto field to save space.

[David S. Miller]

On Wed, 21 Apr 2004 17:15:12 -0700
Joe Perches <joe@perches.com> wrote:

> On Wed, 2004-04-21 at 11:10, Stephen Hemminger wrote:
> > +	__u8	unused_pad;
> 
> There's no real reason that I can see to have padding here.

SO that the next person adding member to this struct
know it exists.