stat: update description of clat accounting in stat.h

[fio.git] / stat.h

diff --git a/stat.h b/stat.h
index 848331bb5e47fef2438cf19a910fed5c02b712bc..3fda084156bbfb984d34985e686a33ad3bb44082 100644 (file)
--- a/stat.h
+++ b/stat.h
@@ -23,6 +23,16 @@ struct group_run_stats {
 #define FIO_IO_U_LAT_U_NR 10
 #define FIO_IO_U_LAT_M_NR 12
 
+/*
+ * Constants for clat percentiles
+ */
+#define FIO_IO_U_PLAT_BITS 6
+#define FIO_IO_U_PLAT_VAL (1 << FIO_IO_U_PLAT_BITS)
+#define FIO_IO_U_PLAT_GROUP_NR 29
+#define FIO_IO_U_PLAT_NR (FIO_IO_U_PLAT_GROUP_NR * FIO_IO_U_PLAT_VAL)
+#define FIO_IO_U_LIST_MAX_LEN 20 /* The size of the default and user-specified
+                                       list of percentiles */
+
 /*
  * Aggregate clat samples to report percentile(s) of them.
  *
@@ -34,7 +44,7 @@ struct group_run_stats {
  *
  * FIO_IO_U_PLAT_GROUP_NR and FIO_IO_U_PLAT_BITS determine the maximum
  * range being tracked for latency samples. The maximum value tracked
- * accurately will be 2^(GROUP_NR + PLAT_BITS -1) microseconds.
+ * accurately will be 2^(GROUP_NR + PLAT_BITS - 1) nanoseconds.
  *
  * FIO_IO_U_PLAT_GROUP_NR and FIO_IO_U_PLAT_BITS determine the memory
  * requirement of storing those aggregate counts. The memory used will
@@ -98,22 +108,15 @@ struct group_run_stats {
  *     3       8       2               [256,511]               64
  *     4       9       3               [512,1023]              64
  *     ...     ...     ...             [...,...]               ...
- *     18      23      17              [8838608,+inf]**        64
+ *     28      33      27              [8589934592,+inf]**     64
  *
  *  * Special cases: when n < (M-1) or when n == (M-1), in both cases,
  *    the value cannot be rounded off. Use all bits of the sample as
  *    index.
  *
- *  ** If a sample's MSB is greater than 23, it will be counted as 23.
+ *  ** If a sample's MSB is greater than 33, it will be counted as 33.
  */
 
-#define FIO_IO_U_PLAT_BITS 6
-#define FIO_IO_U_PLAT_VAL (1 << FIO_IO_U_PLAT_BITS)
-#define FIO_IO_U_PLAT_GROUP_NR 29
-#define FIO_IO_U_PLAT_NR (FIO_IO_U_PLAT_GROUP_NR * FIO_IO_U_PLAT_VAL)
-#define FIO_IO_U_LIST_MAX_LEN 20 /* The size of the default and user-specified
-                                       list of percentiles */
-
 /*
  * Trim cycle count measurements
  */