Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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 <rusty@rustcorp.com.au>
+11
-1
Documentation/lguest/lguest.c
+11
-1
Documentation/lguest/lguest.c
···
84
84
static unsigned long guest_limit, guest_max;
85
85
/* The pipe for signal hander to write to. */
86
86
static int timeoutpipe[2];
87
+
static unsigned int timeout_usec = 500;
87
88
88
89
/* a per-cpu variable indicating whose vcpu is currently running */
89
90
static unsigned int __thread cpu_id;
···
906
905
itm.it_interval.tv_sec = 0;
907
906
itm.it_interval.tv_usec = 0;
908
907
itm.it_value.tv_sec = 0;
909
-
itm.it_value.tv_usec = 500;
908
+
itm.it_value.tv_usec = timeout_usec;
910
909
911
910
setitimer(ITIMER_REAL, &itm, NULL);
912
911
}
···
923
922
unsigned int head, out, in, num = 0;
924
923
int len;
925
924
struct iovec iov[vq->vring.num];
925
+
static int last_timeout_num;
926
926
927
927
/* Keep getting output buffers from the Guest until we run out. */
928
928
while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
···
941
939
/* Block further kicks and set up a timer if we saw anything. */
942
940
if (!timeout && num)
943
941
block_vq(vq);
942
+
943
+
if (timeout) {
944
+
if (num < last_timeout_num)
945
+
timeout_usec += 10;
946
+
else if (timeout_usec > 1)
947
+
timeout_usec--;
948
+
last_timeout_num = num;
949
+
}
944
950
}
945
951
946
952
/* This is where we handle a packet coming in from the tun device to our