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

Signed-off-by: Jens Axboe <axboe@kernel.dk>

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

diff --git a/fio.1 b/fio.1
index f54ea34b65b2276c0b2bc2d1e866f185a848ba94..91020b2eeb89a4b5b3d4da3f9ff7f2aa87f668c0 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -702,7 +702,12 @@ Pretend to spend CPU time for given number of microseconds, sleeping the rest
 of the time specified by \fBthinktime\fR.  Only valid if \fBthinktime\fR is set.
 .TP
 .BI thinktime_blocks \fR=\fPint
-Number of blocks to issue before waiting \fBthinktime\fR microseconds.
+Only valid if thinktime is set - control how many blocks to issue, before
+waiting \fBthinktime\fR microseconds. If not set, defaults to 1 which will
+make fio wait \fBthinktime\fR microseconds 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.
 Default: 1.
 .TP
 .BI rate \fR=\fPint