handle kernelcore=: generic

This patch adds the kernelcore= parameter for x86.

Once all patches are applied, a new command-line parameter exist and a new
sysctl.  This patch adds the necessary documentation.

From: Yasunori Goto <y-goto@jp.fujitsu.com>

  When "kernelcore" boot option is specified, kernel can't boot up on ia64
  because of an infinite loop.  In addition, the parsing code can be handled
  in an architecture-independent manner.

  This patch uses common code to handle the kernelcore= parameter.  It is
  only available to architectures that support arch-independent zone-sizing
  (i.e.  define CONFIG_ARCH_POPULATES_NODE_MAP).  Other architectures will
  ignore the boot parameter.

[bunk@stusta.de: make cmdline_parse_kernelcore() static]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Acked-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 33 insertions, 1 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 460b892d089e..ebffdffb3d99 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1348,6 +1348,21 @@ nr_hugepages configures number of hugetlb page reserved for the system.
 hugetlb_shm_group contains group id that is allowed to create SysV shared
 memory segment using hugetlb page.
 
+hugepages_treat_as_movable
+--------------------------
+
+This parameter is only useful when kernelcore= is specified at boot time to
+create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
+are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
+value written to hugepages_treat_as_movable allows huge pages to be allocated
+from ZONE_MOVABLE.
+
+Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
+pages pool can easily grow or shrink within. Assuming that applications are
+not running that mlock() a lot of memory, it is likely the huge pages pool
+can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
+into nr_hugepages and triggering page reclaim.
+
 laptop_mode
 -----------
 
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 8363ad3ba018..1794affbd06f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -817,6 +817,22 @@ and is between 256 and 4096 characters. It is defined in the file
         js=             [HW,JOY] Analog joystick
                         See Documentation/input/joystick.txt.
 
+        kernelcore=nn[KMG]      [KNL,IA-32,IA-64,PPC,X86-64] This parameter
+                        specifies the amount of memory usable by the kernel
+                        for non-movable allocations.  The requested amount is
+                        spread evenly throughout all nodes in the system. The
+                        remaining memory in each node is used for Movable
+                        pages. In the event, a node is too small to have both
+                        kernelcore and Movable pages, kernelcore pages will
+                        take priority and other nodes will have a larger number
+                        of kernelcore pages.  The Movable zone is used for the
+                        allocation of pages that may be reclaimed or moved
+                        by the page migration subsystem.  This means that
+                        HugeTLB pages may not be allocated from this zone.
+                        Note that allocations like PTEs-from-HighMem still
+                        use the HighMem zone if it exists, and the Normal
+                        zone if it does not.
+
         keepinitrd      [HW,ARM]
 
         kstack=N        [IA-32,X86-64] Print N words from the kernel stack
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index df3ff2095f9d..a0ccc5b60260 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -38,7 +38,8 @@ Currently, these files are in /proc/sys/vm:
 
 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
 dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
-block_dump, swap_token_timeout, drop-caches:
+block_dump, swap_token_timeout, drop-caches,
+hugepages_treat_as_movable:
 
 See Documentation/filesystems/proc.txt