FreeBSD build broken due to missing -lrt

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index d3639fb487d2c3fa206b1789ad59132e12e83e0c..dc21afc039d36456e41ea215b4c2917274ecc74f 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -549,7 +549,14 @@ ioengine=str       Defines how the job issues io to the file. The following
 iodepth=int    This defines how many io units to keep in flight against
                the file. The default is 1 for each file defined in this
                job, can be overridden with a larger value for higher
-               concurrency.
+               concurrency. Note that increasing iodepth beyond 1 will not
+               affect synchronous ioengines (except for small degress when
+               verify_async is in use). Even async engines my impose OS
+               restrictions causing the desired depth not to be achieved.
+               This may happen on Linux when using libaio and not setting
+               direct=1, since buffered IO is not async on that OS. Keep an
+               eye on the IO depth distribution in the fio output to verify
+               that the achieved depth is as expected. Default: 1.
 
 iodepth_batch_submit=int
 iodepth_batch=int This defines how many pieces of IO to submit at once.
@@ -935,13 +942,18 @@ verify_backlog=int        Fio will normally verify the written contents of a
                associated with an IO block in memory, so for large
                verify workloads, quite a bit of memory would be used up
                holding this meta data. If this option is enabled, fio
+               will write only N blocks before verifying these blocks.
+
                will verify the previously written blocks before continuing
                to write new ones.
 
 verify_backlog_batch=int       Control how many blocks fio will verify
                if verify_backlog is set. If not set, will default to
                the value of verify_backlog (meaning the entire queue
-               is read back and verified).
+               is read back and verified).  If verify_backlog_batch is
+               less than verify_backlog then not all blocks will be verified,
+               if verify_backlog_batch is larger than verify_backlog, some
+               blocks will be verified more than once.
                
 stonewall      Wait for preceeding jobs in the job file to exit, before
                starting this one. Can be used to insert serialization
@@ -1287,4 +1299,4 @@ Split up, the format is as follows:
        IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
        Additional Info (dependant on continue_on_error, default off): total # errors, first error code 
        
-       Additional Info (dependant on description being set): Text description
\ No newline at end of file
+       Additional Info (dependant on description being set): Text description