| Message ID | 20100124215001.78251e25@nehalam |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Stephen Hemminger <shemminger@vyatta.com> Date: Sun, 24 Jan 2010 21:50:01 -0800 > @@ -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; > } > > /* Hmmm... When the ring is full head==tail, which means tcp_probe_used() returns 0. Which would now make tcp_probe_avail() return "bufsize - 0 - 1". Is that right? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, 24 Jan 2010 22:41:22 -0800 (PST) David Miller <davem@davemloft.net> wrote: > From: Stephen Hemminger <shemminger@vyatta.com> > Date: Sun, 24 Jan 2010 21:50:01 -0800 > > > @@ -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; > > } > > > > /* > > Hmmm... When the ring is full head==tail, which means > tcp_probe_used() returns 0. Which would now make tcp_probe_avail() > return "bufsize - 0 - 1". > > Is that right? Yes. in this ring; empty is head == tail, and full needs to be tail == head - 1.
From: Stephen Hemminger <shemminger@vyatta.com> Date: Mon, 25 Jan 2010 08:30:06 -0800 > On Sun, 24 Jan 2010 22:41:22 -0800 (PST) > David Miller <davem@davemloft.net> wrote: > >> From: Stephen Hemminger <shemminger@vyatta.com> >> Date: Sun, 24 Jan 2010 21:50:01 -0800 >> >> > @@ -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; >> > } >> > >> > /* >> >> Hmmm... When the ring is full head==tail, which means >> tcp_probe_used() returns 0. Which would now make tcp_probe_avail() >> return "bufsize - 0 - 1". >> >> Is that right? > > Yes. in this ring; empty is head == tail, and full needs to > be tail == head - 1. Ok, that makes sense, thanks for explaining. Applied, thanks Stephen. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/net/ipv4/tcp_probe.c 2010-01-24 21:43:07.069894439 -0800 +++ b/net/ipv4/tcp_probe.c 2010-01-24 21:46:15.301153066 -0800 @@ -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 s 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 * 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 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);
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> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html