Add a bit of huge page documentation

[fio.git] / fio.1

diff --git a/fio.1 b/fio.1
index 10b1768ce42e9eb712f77202549c0b76795695ad..f216b4cb00c2665796826d37c5df159973b5fe16 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -515,7 +515,11 @@ Same as \fBmmap\fR, but use huge files as backing.
 The amount of memory allocated is the maximum allowed \fBblocksize\fR for the
 job multiplied by \fBiodepth\fR.  For \fBshmhuge\fR or \fBmmaphuge\fR to work,
 the system must have free huge pages allocated.  \fBmmaphuge\fR also needs to
-have hugetlbfs mounted, and \fIfile\fR must point there.
+have hugetlbfs mounted, and \fIfile\fR must point there. At least on Linux,
+huge pages must be manually allocated. See \fB/proc/sys/vm/nr_hugehages\fR
+and the documentation for that. Normally you just need to echo an appropriate
+number, eg echoing 8 will ensure that the OS has 8 huge pages ready for
+use.
 .RE
 .TP
 .BI iomem_align \fR=\fPint