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Commit f81074f8 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
Browse files

tcp_probe: avoid modulus operation and wrap fix 



By rounding up the buffer size to power of 2, several expensive
modulus operations can be avoided.  This patch also solves a bug where
the gap need when ring gets full was not being accounted for.

Signed-off-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4f9a91c8

net/ipv4/tcp_probe.c

+10 −9
Original line number Original line Diff line number Diff line
@@ -39,9 +39,9 @@ static int port __read_mostly = 0; 
MODULE_PARM_DESC(port, "Port to match (0=all)");

MODULE_PARM_DESC(port, "Port to match (0=all)");

module_param(port, int, 0);

module_param(port, int, 0);





static int bufsize __read_mostly = 4096;

static unsigned int bufsize __read_mostly = 4096;

MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");

MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");

module_param(bufsize, int, 0);

module_param(bufsize, uint, 0);





static int full __read_mostly;

static int full __read_mostly;

MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");

MODULE_PARM_DESC(full, "Full log (1=every ack packet received,  0=only cwnd changes)");
@@ -75,12 +75,12 @@ static struct { 




static inline int tcp_probe_used(void)

static inline int tcp_probe_used(void)

{

{

	return (tcp_probe.head - tcp_probe.tail) % bufsize;

	return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);

}

}





static inline int tcp_probe_avail(void)

static inline int tcp_probe_avail(void)

{

{

	return bufsize - tcp_probe_used();

	return bufsize - tcp_probe_used() - 1;

}

}





/*

/*
@@ -116,7 +116,7 @@ static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb, 
			p->ssthresh = tcp_current_ssthresh(sk);

			p->ssthresh = tcp_current_ssthresh(sk);

			p->srtt = tp->srtt >> 3;

			p->srtt = tp->srtt >> 3;





			tcp_probe.head = (tcp_probe.head + 1) % bufsize;

			tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);

		}

		}

		tcp_probe.lastcwnd = tp->snd_cwnd;

		tcp_probe.lastcwnd = tp->snd_cwnd;

		spin_unlock(&tcp_probe.lock);

		spin_unlock(&tcp_probe.lock);
@@ -149,7 +149,7 @@ static int tcpprobe_open(struct inode * inode, struct file * file) 
static int tcpprobe_sprint(char *tbuf, int n)

static int tcpprobe_sprint(char *tbuf, int n)

{

{

	const struct tcp_log *p

	const struct tcp_log *p

		= tcp_probe.log + tcp_probe.tail % bufsize;

		= tcp_probe.log + tcp_probe.tail;

	struct timespec tv

	struct timespec tv

		= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));

		= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
@@ -192,7 +192,7 @@ static ssize_t tcpprobe_read(struct file *file, char __user *buf, 
		width = tcpprobe_sprint(tbuf, sizeof(tbuf));

		width = tcpprobe_sprint(tbuf, sizeof(tbuf));





		if (cnt + width < len)

		if (cnt + width < len)

			tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;

			tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);





		spin_unlock_bh(&tcp_probe.lock);

		spin_unlock_bh(&tcp_probe.lock);
@@ -222,9 +222,10 @@ static __init int tcpprobe_init(void) 
	init_waitqueue_head(&tcp_probe.wait);

	init_waitqueue_head(&tcp_probe.wait);

	spin_lock_init(&tcp_probe.lock);

	spin_lock_init(&tcp_probe.lock);





	if (bufsize < 0)

	if (bufsize == 0)

		return -EINVAL;

		return -EINVAL;





	bufsize = roundup_pow_of_two(bufsize);

	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);

	tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);

	if (!tcp_probe.log)

	if (!tcp_probe.log)

		goto err0;

		goto err0;
@@ -236,7 +237,7 @@ static __init int tcpprobe_init(void) 
	if (ret)

	if (ret)

		goto err1;

		goto err1;





	pr_info("TCP probe registered (port=%d)\n", port);

	pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize);

	return 0;

	return 0;

 err1:

 err1:

	proc_net_remove(&init_net, procname);

	proc_net_remove(&init_net, procname);