[PATCH] Support for mmap of hugetlb files as memory backing

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 1e1f4097f54218e8c9d70e9479aecc9bf62c635d..f5e2449c22d64956015d983c04c1f93aa8dc9840 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -224,7 +224,9 @@ bs=siint    The block size used for the io units. Defaults to 4k. Values
                after a comma, it will apply to writes only. In other words,
                the format is either bs=read_and_write or bs=read,write.
                bs=4k,8k will thus use 4k blocks for reads, and 8k blocks
-               for writes.
+               for writes. If you only wish to set the write size, you
+               can do so by passing an empty read size - bs=,8k will set
+               8k for writes and leave the read default value.
 
 bsrange=irange Instead of giving a single block size, specify a range
                and fio will mix the issued io block sizes. The issued
@@ -262,6 +264,10 @@ ioengine=str       Defines how the job issues io to the file. The following
                                we use read(2) and write(2) for asynchronous
                                io.
 
+                       null    Doesn't transfer any data, just pretends
+                               to. This is mainly used to exercise fio
+                               itself and for debugging/testing purposes.
+
 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
@@ -351,9 +357,15 @@ mem=str            Fio can use various types of memory as the io unit buffer.
                        shm     Use shared memory as the buffers. Allocated
                                through shmget(2).
 
+                       shmhuge Same as shm, but use huge pages as backing.
+
                        mmap    Use anonymous memory maps as the buffers.
                                Allocated through mmap(2).
 
+                       mmaphuge Use a memory mapped huge file as the buffer
+                               backing. Append filename after mmaphuge, ala
+                               mem=mmaphuge:/hugetlbfs/file
+
                The area allocated is a function of the maximum allowed
                bs size for the job, multiplied by the io depth given.