[PATCH v2 5/5] docs: update discussion of huge page sizes

[Vincent Fu <vincent.fu@samsung.com>]

Note that the default huge page size is either 2 or 4 MiB, depending on
the platform. Also mention /sys/kernel/mm/hugepages/ as another place to
see the supported huge page sizes.

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
---
 HOWTO.rst | 25 ++++++++++++++-----------
 fio.1     | 19 ++++++++++---------
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/HOWTO.rst b/HOWTO.rst
index eee386c1..58d02fa2 100644
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -1823,13 +1823,14 @@ Buffers and memory
 	**mmaphuge** to work, the system must have free huge pages allocated. This
 	can normally be checked and set by reading/writing
 	:file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
-	is 4MiB in size. So to calculate the number of huge pages you need for a
-	given job file, add up the I/O depth of all jobs (normally one unless
-	:option:`iodepth` is used) and multiply by the maximum bs set. Then divide
-	that number by the huge page size. You can see the size of the huge pages in
-	:file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero
-	number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also
-	see :option:`hugepage-size`.
+        is 2 or 4MiB in size depending on the platform. So to calculate the
+        number of huge pages you need for a given job file, add up the I/O
+        depth of all jobs (normally one unless :option:`iodepth` is used) and
+        multiply by the maximum bs set. Then divide that number by the huge
+        page size. You can see the size of the huge pages in
+        :file:`/proc/meminfo`. If no huge pages are allocated by having a
+        non-zero number in `nr_hugepages`, using **mmaphuge** or **shmhuge**
+        will fail. Also see :option:`hugepage-size`.
 
 	**mmaphuge** also needs to have hugetlbfs mounted and the file location
 	should point there. So if it's mounted in :file:`/huge`, you would use
@@ -1848,10 +1849,12 @@ Buffers and memory
 
 .. option:: hugepage-size=int
 
-	Defines the size of a huge page. Must at least be equal to the system
-	setting, see :file:`/proc/meminfo`. Defaults to 4MiB.  Should probably
-	always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the
-	preferred way to set this to avoid setting a non-pow-2 bad value.
+        Defines the size of a huge page. Must at least be equal to the system
+        setting, see :file:`/proc/meminfo` and
+        :file:`/sys/kernel/mm/hugepages/`. Defaults to 2 or 4MiB depending on
+        the platform.  Should probably always be a multiple of megabytes, so
+        using ``hugepage-size=Xm`` is the preferred way to set this to avoid
+        setting a non-pow-2 bad value.
 
 .. option:: lockmem=int
 
diff --git a/fio.1 b/fio.1
index ded7bbfc..5f057574 100644
--- a/fio.1
+++ b/fio.1
@@ -1631,11 +1631,11 @@ multiplied by the I/O depth given. Note that for \fBshmhuge\fR and
 \fBmmaphuge\fR to work, the system must have free huge pages allocated. This
 can normally be checked and set by reading/writing
 `/proc/sys/vm/nr_hugepages' on a Linux system. Fio assumes a huge page
-is 4MiB in size. So to calculate the number of huge pages you need for a
-given job file, add up the I/O depth of all jobs (normally one unless
-\fBiodepth\fR is used) and multiply by the maximum bs set. Then divide
-that number by the huge page size. You can see the size of the huge pages in
-`/proc/meminfo'. If no huge pages are allocated by having a non-zero
+is 2 or 4MiB in size depending on the platform. So to calculate the number of
+huge pages you need for a given job file, add up the I/O depth of all jobs
+(normally one unless \fBiodepth\fR is used) and multiply by the maximum bs set.
+Then divide that number by the huge page size. You can see the size of the huge
+pages in `/proc/meminfo'. If no huge pages are allocated by having a non-zero
 number in `nr_hugepages', using \fBmmaphuge\fR or \fBshmhuge\fR will fail. Also
 see \fBhugepage\-size\fR.
 .P
@@ -1655,10 +1655,11 @@ of subsequent I/O memory buffers is the sum of the \fBiomem_align\fR and
 \fBbs\fR used.
 .TP
 .BI hugepage\-size \fR=\fPint
-Defines the size of a huge page. Must at least be equal to the system
-setting, see `/proc/meminfo'. Defaults to 4MiB. Should probably
-always be a multiple of megabytes, so using `hugepage\-size=Xm' is the
-preferred way to set this to avoid setting a non-pow-2 bad value.
+Defines the size of a huge page. Must at least be equal to the system setting,
+see `/proc/meminfo' and `/sys/kernel/mm/hugepages/'. Defaults to 2 or 4MiB
+depending on the platform. Should probably always be a multiple of megabytes,
+so using `hugepage\-size=Xm' is the preferred way to set this to avoid setting
+a non-pow-2 bad value.
 .TP
 .BI lockmem \fR=\fPint
 Pin the specified amount of memory with \fBmlock\fR\|(2). Can be used to
-- 
2.25.1