MFcalloutng:

Make dcons input polling adaptive, reducing poll rate to 1Hz after several
minutes of inactivty to reduce global interrupt rate.  Most of users never
used FireWire debugging, so it is not very useful to consume power by it.

1 files changed, 12 insertions, 6 deletions

diff --git a/sys/dev/dcons/dcons_os.c b/sys/dev/dcons/dcons_os.c
index a37d64c8706c..bf0be0b29cbc 100644
--- a/sys/dev/dcons/dcons_os.c
+++ b/sys/dev/dcons/dcons_os.c
@@ -74,6 +74,10 @@
 #define DCONS_POLL_HZ	25
 #endif
 
+#ifndef DCONS_POLL_IDLE
+#define DCONS_POLL_IDLE	256
+#endif
+
 #ifndef DCONS_BUF_SIZE
 #define DCONS_BUF_SIZE (16*1024)
 #endif
@@ -90,6 +94,7 @@ static char bssbuf[DCONS_BUF_SIZE];	/* buf in bss */
 static struct dcons_global dg;
 struct dcons_global *dcons_conf;
 static int poll_hz = DCONS_POLL_HZ;
+static u_int poll_idle = DCONS_POLL_HZ * DCONS_POLL_IDLE;
 
 static struct dcons_softc sc[DCONS_NPORT];
 
@@ -214,14 +219,17 @@ dcons_timeout(void *v)
 		tp = dc->tty;
 
 		tty_lock(tp);
-		while ((c = dcons_os_checkc_nopoll(dc)) != -1)
+		while ((c = dcons_os_checkc_nopoll(dc)) != -1) {
 			ttydisc_rint(tp, c, 0);
+			poll_idle = 0;
+		}
 		ttydisc_rint_done(tp);
 		tty_unlock(tp);
 	}
-	polltime = hz / poll_hz;
-	if (polltime < 1)
-		polltime = 1;
+	poll_idle++;
+	polltime = hz;
+	if (poll_idle <= (poll_hz * DCONS_POLL_IDLE))
+		polltime /= poll_hz;
 	callout_reset(&dcons_callout, polltime, dcons_timeout, tp);
 }
 
@@ -368,8 +376,6 @@ dcons_attach(void)
 	dcons_attach_port(DCONS_GDB, "dgdb", DC_GDB);
 	callout_init(&dcons_callout, CALLOUT_MPSAFE);
 	polltime = hz / poll_hz;
-	if (polltime < 1)
-		polltime = 1;
 	callout_reset(&dcons_callout, polltime, dcons_timeout, NULL);
 	return(0);
 }