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Date:      Fri, 14 Dec 2012 23:13:07 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-projects@freebsd.org
Subject:   svn commit: r244235 - projects/calloutng/sys/dev/dcons
Message-ID:  <201212142313.qBEND7kw074246@svn.freebsd.org>
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Author: mav
Date: Fri Dec 14 23:13:06 2012
New Revision: 244235
URL: http://svnweb.freebsd.org/changeset/base/244235

Log:
  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:
  projects/calloutng/sys/dev/dcons/dcons_os.c

Modified: projects/calloutng/sys/dev/dcons/dcons_os.c
==============================================================================
--- projects/calloutng/sys/dev/dcons/dcons_os.c	Fri Dec 14 23:07:25 2012	(r244234)
+++ projects/calloutng/sys/dev/dcons/dcons_os.c	Fri Dec 14 23:13:06 2012	(r244235)
@@ -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);
 }

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