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[linux-2.6.git] / include / linux / time.h

diff --git a/include/linux/time.h b/include/linux/time.h
index b85d596..3300f90 100644 (file)
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -177,6 +177,34 @@ struct timezone {
        (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
 
 #endif
+
+/*
+ * Convert jiffies to milliseconds and back.
+ *
+ * Avoid unnecessary multiplications/divisions in the
+ * two most common HZ cases:
+ */
+static inline unsigned int jiffies_to_msecs(unsigned long j)
+{
+#if HZ <= 1000 && !(1000 % HZ)
+       return (1000 / HZ) * j;
+#elif HZ > 1000 && !(HZ % 1000)
+       return (j + (HZ / 1000) - 1)/(HZ / 1000);
+#else
+       return (j * 1000) / HZ;
+#endif
+}
+static inline unsigned long msecs_to_jiffies(unsigned int m)
+{
+#if HZ <= 1000 && !(1000 % HZ)
+       return (m + (1000 / HZ) - 1) / (1000 / HZ);
+#elif HZ > 1000 && !(HZ % 1000)
+       return m * (HZ / 1000);
+#else
+       return (m * HZ + 999) / 1000;
+#endif
+}
+
 /*
  * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
  * that a remainder subtract here would not do the right thing as the