From f81074f86176605bfbfafb9944e27628a4e26ce6 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Mon, 25 Jan 2010 15:47:50 -0800 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/ipv4/tcp_probe.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/ipv4/tcp_probe.c b/net/ipv4/tcp_probe.c index bb110c5..9bc805d 100644 --- a/net/ipv4/tcp_probe.c +++ b/net/ipv4/tcp_probe.c @@ -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); -- 1.8.2.3