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Subject[PATCH 14/14] x86-32, NUMA: Update remap allocator comments
Date
Now that remap allocator is cleaned up, update comments such that they
are in docbook function description format and reflect the actual
implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
arch/x86/mm/numa_32.c | 56 ++++++++++++++++++++++++++++++++++++------------
1 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/arch/x86/mm/numa_32.c b/arch/x86/mm/numa_32.c
index f325e6f..c757c0a 100644
--- a/arch/x86/mm/numa_32.c
+++ b/arch/x86/mm/numa_32.c
@@ -176,17 +176,31 @@ static void __init allocate_pgdat(int nid)
}

/*
- * In the DISCONTIGMEM and SPARSEMEM memory model, a portion of the kernel
- * virtual address space (KVA) is reserved and portions of nodes are mapped
- * using it. This is to allow node-local memory to be allocated for
- * structures that would normally require ZONE_NORMAL. The memory is
- * allocated with alloc_remap() and callers should be prepared to allocate
- * from the bootmem allocator instead.
+ * Remap memory allocator
*/
static unsigned long node_remap_start_pfn[MAX_NUMNODES];
static void *node_remap_end_vaddr[MAX_NUMNODES];
static void *node_remap_alloc_vaddr[MAX_NUMNODES];

+/**
+ * alloc_remap - Allocate remapped memory
+ * @nid: NUMA node to allocate memory from
+ * @size: The size of allocation
+ *
+ * Allocate @size bytes from the remap area of NUMA node @nid. The
+ * size of the remap area is predetermined by init_alloc_remap() and
+ * only the callers considered there should call this function. For
+ * more info, please read the comment on top of init_alloc_remap().
+ *
+ * The caller must be ready to handle allocation failure from this
+ * function and fall back to regular memory allocator in such cases.
+ *
+ * CONTEXT:
+ * Single CPU early boot context.
+ *
+ * RETURNS:
+ * Pointer to the allocated memory on success, %NULL on failure.
+ */
void *alloc_remap(int nid, unsigned long size)
{
void *allocation = node_remap_alloc_vaddr[nid];
@@ -238,6 +252,28 @@ void resume_map_numa_kva(pgd_t *pgd_base)
}
#endif

+/**
+ * init_alloc_remap - Initialize remap allocator for a NUMA node
+ * @nid: NUMA node to initizlie remap allocator for
+ *
+ * NUMA nodes may end up without any lowmem. As allocating pgdat and
+ * memmap on a different node with lowmem is inefficient, a special
+ * remap allocator is implemented which can be used by alloc_remap().
+ *
+ * For each node, the amount of memory which will be necessary for
+ * pgdat and memmap is calculated and two memory areas of the size are
+ * allocated - one in the node and the other in lowmem; then, the area
+ * in the node is remapped to the lowmem area.
+ *
+ * As pgdat and memmap must be allocated in lowmem anyway, this
+ * doesn't waste lowmem address space; however, the actual lowmem
+ * which gets remapped over is wasted. The amount shouldn't be
+ * problematic on machines this feature will be used.
+ *
+ * Initialization failure isn't fatal. alloc_remap() is used
+ * opportunistically and the callers will fall back to other memory
+ * allocation mechanisms on failure.
+ */
static __init void init_alloc_remap(int nid)
{
unsigned long size, pfn;
@@ -306,14 +342,6 @@ void __init initmem_init(void)
{
int nid;

- /*
- * When mapping a NUMA machine we allocate the node_mem_map arrays
- * from node local memory. They are then mapped directly into KVA
- * between zone normal and vmalloc space. Calculate the size of
- * this space and use it to adjust the boundary between ZONE_NORMAL
- * and ZONE_HIGHMEM.
- */
-
get_memcfg_numa();
numa_init_array();

--
1.7.1


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