Update HOWTO and man page for thinktime blocks impact on queue depth

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 9b2edb37501c71eed82871f2e51cdaed2b9388fd..794728f3b2cf3b3d9edc3a7493ce157c8a5901ea 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -830,11 +830,15 @@ thinktime_spin=int
                to sleeping for the rest of the period specified by
                thinktime.
 
-thinktime_blocks
+thinktime_blocks=int
                Only valid if thinktime is set - control how many blocks
                to issue, before waiting 'thinktime' usecs. If not set,
                defaults to 1 which will make fio wait 'thinktime' usecs
-               after every block.
+               after every block. This effectively makes any queue depth
+               setting redundant, since no more than 1 IO will be queued
+               before we have to complete it and do our thinktime. In
+               other words, this setting effectively caps the queue depth
+               if the latter is larger.
 
 rate=int       Cap the bandwidth used by this job. The number is in bytes/sec,
                the normal suffix rules apply. You can use rate=500k to limit