hugetlb: override default huge page size

Allow configurations with the default huge page size which is different to
the traditional HPAGE_SIZE size.  The default huge page size is the one
represented in the legacy /proc ABIs, SHM, and which is defaulted to when
mounting hugetlbfs filesystems.

This is implemented with a new kernel option default_hugepagesz=, which
defaults to HPAGE_SIZE if not specified.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d55fd88fd0a9..30278e9e5211 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -783,6 +783,13 @@ and is between 256 and 4096 characters. It is defined in the file
                         CPU supports the "pdpe1gb" cpuinfo flag)
                         Note that 1GB pages can only be allocated at boot time
                         using hugepages= and not freed afterwards.
+        default_hugepagesz=
+                        [same as hugepagesz=] The size of the default
+                        HugeTLB page size. This is the size represented by
+                        the legacy /proc/ hugepages APIs, used for SHM, and
+                        default size when mounting hugetlbfs filesystems.
+                        Defaults to the default architecture's huge page size
+                        if not specified.
 
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