Subject: [PATCH 1/2] pkt_sched: Use PSCHED_SHIFT in PSCHED time conversion

From: Jarek Poplawski <[email-masked]>
Date: Tue, 9 Jun 2009 08:05:00 +0000

Use PSCHED_SHIFT constant instead of '10' in PSCHED_US2NS() and
PSCHED_NS2US() macros to enable changing this value later.

Additionally use PSCHED_SHIFT in sch_hfsc SM_SHIFT and ISM_SHIFT
definitions. This part of the patch is based on feedback from
Patrick McHardy <[email-masked]>.

Reported-by: Antonio Almeida <[email-masked]>
Tested-by: Antonio Almeida <[email-masked]>
Signed-off-by: Jarek Poplawski <[email-masked]>
---

 include/net/pkt_sched.h |    5 +++--
 net/sched/sch_hfsc.c    |    8 +++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index e37fe31..cd0e026 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -42,8 +42,9 @@ typedef u64	psched_time_t;
 typedef long	psched_tdiff_t;
 
 /* Avoid doing 64 bit divide by 1000 */
-#define PSCHED_US2NS(x)			((s64)(x) << 10)
-#define PSCHED_NS2US(x)			((x) >> 10)
+#define PSCHED_SHIFT			10
+#define PSCHED_US2NS(x)			((s64)(x) << PSCHED_SHIFT)
+#define PSCHED_NS2US(x)			((x) >> PSCHED_SHIFT)
 
 #define PSCHED_TICKS_PER_SEC		PSCHED_NS2US(NSEC_PER_SEC)
 #define PSCHED_PASTPERFECT		0
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 5022f9c..362c281 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -372,7 +372,7 @@ cftree_update(struct hfsc_class *cl)
  *	ism: (psched_us/byte) << ISM_SHIFT
  *	dx: psched_us
  *
- * The clock source resolution with ktime is 1.024us.
+ * The clock source resolution with ktime and PSCHED_SHIFT 10 is 1.024us.
  *
  * sm and ism are scaled in order to keep effective digits.
  * SM_SHIFT and ISM_SHIFT are selected to keep at least 4 effective
@@ -383,9 +383,11 @@ cftree_update(struct hfsc_class *cl)
  *  bytes/1.024us 12.8e-3    128e-3     1280e-3    12800e-3   128000e-3
  *
  *  1.024us/byte  78.125     7.8125     0.78125    0.078125   0.0078125
+ *
+ * So, for PSCHED_SHIFT 10 we need: SM_SHIFT 20, ISM_SHIFT 18.
  */
-#define	SM_SHIFT	20
-#define	ISM_SHIFT	18
+#define	SM_SHIFT	(30 - PSCHED_SHIFT)
+#define	ISM_SHIFT	(8 + PSCHED_SHIFT)
 
 #define	SM_MASK		((1ULL << SM_SHIFT) - 1)
 #define	ISM_MASK	((1ULL << ISM_SHIFT) - 1)