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From: Alexander Motin <mav@FreeBSD.org>
Date: Tue, 19 Feb 2013 18:22:25 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r247005 - head/sys/dev/dcons
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Author: mav
Date: Tue Feb 19 18:22:25 2013
New Revision: 247005
URL: http://svnweb.freebsd.org/changeset/base/247005

Log:
  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.

Modified:
  head/sys/dev/dcons/dcons_os.c

Modified: head/sys/dev/dcons/dcons_os.c
==============================================================================
--- head/sys/dev/dcons/dcons_os.c	Tue Feb 19 17:57:17 2013	(r247004)
+++ head/sys/dev/dcons/dcons_os.c	Tue Feb 19 18:22:25 2013	(r247005)
@@ -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];	/* b
 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);
 }