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linux-sg2042
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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: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2010-01-25 15:47:50 -08:00 committed by David S. Miller
parent 4f9a91c812
commit f81074f861
1 changed files with 10 additions and 9 deletions
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19
net/ipv4/tcp_probe.c
View File

@ -39,9 +39,9 @@ static int port __read_mostly = 0;
MODULE_PARM_DESC(port, "Port to match (0=all)");
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_param(bufsize, int, 0);
module_param(bufsize, uint, 0);
static int full __read_mostly;
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)
{
return (tcp_probe.head - tcp_probe.tail) % bufsize;
return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
}
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->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;
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)
{
const struct tcp_log *p
= tcp_probe.log + tcp_probe.tail % bufsize;
= tcp_probe.log + tcp_probe.tail;
struct timespec tv
= 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));
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);
@ -222,9 +222,10 @@ static __init int tcpprobe_init(void)
init_waitqueue_head(&tcp_probe.wait);
spin_lock_init(&tcp_probe.lock);
if (bufsize < 0)
if (bufsize == 0)
return -EINVAL;
bufsize = roundup_pow_of_two(bufsize);
tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
if (!tcp_probe.log)
goto err0;
@ -236,7 +237,7 @@ static __init int tcpprobe_init(void)
if (ret)
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;
err1:
proc_net_remove(&init_net, procname);