svn commit: r242846 - in projects/calloutng/sys: kern sys

[Davide Italiano]

Author: davide
Date: Sat Nov 10 02:08:19 2012
New Revision: 242846
URL: http://svnweb.freebsd.org/changeset/base/242846

Log:
  - Use absolute value for precision rather than flags. This gives us 24
  bits range (which could be extended up to 31) to specify tolerance
  interval for callout. Also, precision interval is not anymore
  constrained to be a power-of-two.
  
  - Get rid of rounding mechanism for precision in callout_cc_add().
  Recent changes to the branch made it less effective as well as increased
  the cost of the rounding operation itself.
  
  Discussed with:		mav

Modified:
  projects/calloutng/sys/kern/kern_timeout.c
  projects/calloutng/sys/sys/callout.h

Modified: projects/calloutng/sys/kern/kern_timeout.c
==============================================================================
--- projects/calloutng/sys/kern/kern_timeout.c	Sat Nov 10 01:52:52 2012	(r242845)
+++ projects/calloutng/sys/kern/kern_timeout.c	Sat Nov 10 02:08:19 2012	(r242846)
@@ -170,7 +170,6 @@ struct callout_cpu cc_cpu;
 #define	CC_LOCK(cc)	mtx_lock_spin(&(cc)->cc_lock)
 #define	CC_UNLOCK(cc)	mtx_unlock_spin(&(cc)->cc_lock)
 #define	CC_LOCK_ASSERT(cc)	mtx_assert(&(cc)->cc_lock, MA_OWNED)
-#define	C_PRECISION	0x2
 
 #define FREQ2BT(freq, bt)                                               \
 {                                                                       \
@@ -576,8 +575,8 @@ callout_cc_add(struct callout *c, struct
 {
 	struct bintime bt;
 	uint64_t r_val;
-	int bucket, r_shift;
-	
+	int bucket;
+
 	CC_LOCK_ASSERT(cc);
 	if (bintime_cmp(&to_bintime, &cc->cc_lastscan, <))
 		to_bintime = cc->cc_lastscan;
@@ -589,35 +588,10 @@ callout_cc_add(struct callout *c, struct
 	c->c_func = func;
 	c->c_time = to_bintime;
 	bintime_clear(&c->c_precision);
-	if (flags & C_PRECISION) {
-		r_shift = ((flags >> 2) & PRECISION_RANGE);
-		r_val = (r_shift != 0) ? (uint64_t)1 << (64 - r_shift) : 0;
-		/*
-		 * Round as far as precision specified is coarse (up to 8ms).
-		 * In order to play safe, round to to half of the interval and
-		 * set half precision.
-		 */
-		if (r_shift < 6) {
-			r_val = (r_shift != 0) ? r_val >> 2 :
-			    ((uint64_t)1 << (64 - 1)) - 1;
-			/*
-			 * Round only if c_time is not a multiple of the
-			 * rounding factor.
-			 */
-			if ((c->c_time.frac & r_val) != r_val) {
-				c->c_time.frac |= r_val - 1;
-				c->c_time.frac += 1;
-				if (c->c_time.frac == 0)
-					c->c_time.sec += 1;
-			}
-		}
-		c->c_precision.frac = r_val;
-		CTR6(KTR_CALLOUT, "rounding %d.%08x%08x to %d.%08x%08x",
-		    to_bintime.sec, (u_int) (to_bintime.frac >> 32),
-		    (u_int) (to_bintime.frac & 0xffffffff), c->c_time.sec,
-		    (u_int) (c->c_time.frac >> 32),
-		    (u_int) (c->c_time.frac & 0xffffffff)); 
-	} 
+	r_val = C_PREC2BT(flags);
+	c->c_precision.frac = r_val;
+	CTR3(KTR_CALLOUT, "precision set for %p: 0.%08x%08",
+	    c, (u_int) (r_val >> 32), (u_int) (r_val & 0xffffffff));
 	bucket = get_bucket(&c->c_time);
 	TAILQ_INSERT_TAIL(&cc->cc_callwheel[bucket], c, c_links.tqe);
 	/*

Modified: projects/calloutng/sys/sys/callout.h
==============================================================================
--- projects/calloutng/sys/sys/callout.h	Sat Nov 10 01:52:52 2012	(r242845)
+++ projects/calloutng/sys/sys/callout.h	Sat Nov 10 02:08:19 2012	(r242846)
@@ -51,28 +51,18 @@
 #define	CALLOUT_DIRECT 		0x0100 /* allow exec from hw int context */
 
 #define	C_DIRECT_EXEC		0x0001 /* direct execution of callout */
-#define	C_P1S			0x0002 /* fields related to precision */ 
-#define	C_P500MS		0x0006 	
-#define	C_P250MS		0x000a 	
-#define	C_P125MS		0x000e
-#define	C_P64MS			0x0012
-#define	C_P32MS			0x0016
-#define	C_P16MS			0x001a
-#define	C_P8MS			0x001e
-#define	C_P4MS			0x0022
-#define	C_P2MS			0x0026
-#define	C_P1MS			0x002a
-#define	C_P500US		0x002e
-#define	C_P250US		0x0032
-#define	C_P125US		0x0036
-#define	C_P64US			0x003a
-#define	C_P32US			0x003e
-#define	C_P16US			0x0042
-#define	C_P8US			0x0046
-#define	C_P4US			0x004a
-#define	C_P2US			0x004e
-#define	PRECISION_BITS		7	
-#define	PRECISION_RANGE		((1 << PRECISION_BITS) - 1)	
+#define	C_PRECISIONBITS		24
+#define	C_PRECISIONRANGE	((1 << C_PRECISIONBITS) - 1)	
+#define	C_PRECISIONMASK		(1 << ((32 - C_PRECISIONBITS) - 1))
+#define	C_T2PREC(x)		(((x) * 4294) & C_PRECISIONMASK) 
+#define	C_PREC2BT(x)		((uint64_t)(flags & C_PRECISIONMASK) << 32)
+
+/*
+ * Common values specified for precision.
+ */
+#define	C_P1MS			C_T2PREC(1000)
+#define	C_P10MS			C_T2PREC(10000)
+#define	C_P100MS		C_T2PREC(100000)
 
 struct callout_handle {
 	struct callout *callout;