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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>
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@ -39,9 +39,9 @@ static int port __read_mostly = 0;
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MODULE_PARM_DESC(port, "Port to match (0=all)");
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module_param(port, int, 0);
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static int bufsize __read_mostly = 4096;
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static unsigned int bufsize __read_mostly = 4096;
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MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
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module_param(bufsize, int, 0);
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module_param(bufsize, uint, 0);
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static int full __read_mostly;
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MODULE_PARM_DESC(full, "Full log (1=every ack packet received, 0=only cwnd changes)");
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@ -75,12 +75,12 @@ static struct {
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static inline int tcp_probe_used(void)
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{
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return (tcp_probe.head - tcp_probe.tail) % bufsize;
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return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
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}
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static inline int tcp_probe_avail(void)
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{
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return bufsize - tcp_probe_used();
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return bufsize - tcp_probe_used() - 1;
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}
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/*
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@ -116,7 +116,7 @@ static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
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p->ssthresh = tcp_current_ssthresh(sk);
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p->srtt = tp->srtt >> 3;
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tcp_probe.head = (tcp_probe.head + 1) % bufsize;
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tcp_probe.head = (tcp_probe.head + 1) & (bufsize - 1);
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}
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tcp_probe.lastcwnd = tp->snd_cwnd;
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spin_unlock(&tcp_probe.lock);
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@ -149,7 +149,7 @@ static int tcpprobe_open(struct inode * inode, struct file * file)
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static int tcpprobe_sprint(char *tbuf, int n)
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{
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const struct tcp_log *p
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= tcp_probe.log + tcp_probe.tail % bufsize;
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= tcp_probe.log + tcp_probe.tail;
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struct timespec tv
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= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
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@ -192,7 +192,7 @@ static ssize_t tcpprobe_read(struct file *file, char __user *buf,
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width = tcpprobe_sprint(tbuf, sizeof(tbuf));
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if (cnt + width < len)
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tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;
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tcp_probe.tail = (tcp_probe.tail + 1) & (bufsize - 1);
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spin_unlock_bh(&tcp_probe.lock);
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@ -222,9 +222,10 @@ static __init int tcpprobe_init(void)
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init_waitqueue_head(&tcp_probe.wait);
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spin_lock_init(&tcp_probe.lock);
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if (bufsize < 0)
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if (bufsize == 0)
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return -EINVAL;
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bufsize = roundup_pow_of_two(bufsize);
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tcp_probe.log = kcalloc(bufsize, sizeof(struct tcp_log), GFP_KERNEL);
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if (!tcp_probe.log)
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goto err0;
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@ -236,7 +237,7 @@ static __init int tcpprobe_init(void)
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if (ret)
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goto err1;
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pr_info("TCP probe registered (port=%d)\n", port);
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pr_info("TCP probe registered (port=%d) bufsize=%u\n", port, bufsize);
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return 0;
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err1:
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proc_net_remove(&init_net, procname);
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