lguest: Adaptive timeout Since the correct timeout value varies, use a heuristic which adjusts the timeout depending on how many packets we've seen. This gives slightly worse results, but doesn't need tweaking when GSO is introduced. 500 usec 19.1887 xmit 561141 recv 1 timeout 559657 Dynamic (278) 20.1974 xmit 214510 recv 5 timeout 214491 usec 278 Signed-off-by: Rusty Russell --- Documentation/lguest/lguest.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff -r 69542a65fafd Documentation/lguest/lguest.c --- a/Documentation/lguest/lguest.c Mon Jul 28 11:28:24 2008 +1000 +++ b/Documentation/lguest/lguest.c Mon Jul 28 11:28:47 2008 +1000 @@ -84,6 +84,7 @@ static unsigned long guest_limit, guest_ static unsigned long guest_limit, guest_max; /* The pipe for signal hander to write to. */ static int timeoutpipe[2]; +static unsigned int timeout_usec = 500; /* a per-cpu variable indicating whose vcpu is currently running */ static unsigned int __thread cpu_id; @@ -905,7 +906,7 @@ static void block_vq(struct virtqueue *v itm.it_interval.tv_sec = 0; itm.it_interval.tv_usec = 0; itm.it_value.tv_sec = 0; - itm.it_value.tv_usec = 500; + itm.it_value.tv_usec = timeout_usec; setitimer(ITIMER_REAL, &itm, NULL); } @@ -922,6 +923,7 @@ static void handle_net_output(int fd, st unsigned int head, out, in, num = 0; int len; struct iovec iov[vq->vring.num]; + static int last_timeout_num; /* Keep getting output buffers from the Guest until we run out. */ while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) { @@ -939,6 +941,14 @@ static void handle_net_output(int fd, st /* Block further kicks and set up a timer if we saw anything. */ if (!timeout && num) block_vq(vq); + + if (timeout) { + if (num < last_timeout_num) + timeout_usec += 10; + else if (timeout_usec > 1) + timeout_usec--; + last_timeout_num = num; + } } /* This is where we handle a packet coming in from the tun device to our