On Tue, May 18, 2021 at 6:12 PM Mike Rapoport [off-list ref] wrote:

On Mon, May 17, 2021 at 07:20:42PM +0800, Dong Aisheng wrote:

quoted

The only path to call memory_present() is from memblocks_present().
The struct mem_section **mem_section only needs to be initialized once,
so no need put the initialization/allocation code in memory_present()
which will be called multiple times for each section.

After moving, the 'unlikely' condition statement becomes to be
meaningless as it's only initialized one time, so dropped as well.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 mm/sparse.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 98bfacc763da..df4418c12f04 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c

@@ -254,19 +254,6 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
 {
      unsigned long pfn;

-#ifdef CONFIG_SPARSEMEM_EXTREME
-     if (unlikely(!mem_section)) {
-             unsigned long size, align;
-
-             size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
-             align = 1 << (INTERNODE_CACHE_SHIFT);
-             mem_section = memblock_alloc(size, align);
-             if (!mem_section)
-                     panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
-                           __func__, size, align);
-     }
-#endif

Maybe split this into a helper function and call it directly from
sparse_init()?

Sounds good to me
e.g. sparse_alloc_section_root() called directly from sparse_init().
Thanks for the suggestion

Regards
Aisheng

quoted

-
      start &= PAGE_SECTION_MASK;
      mminit_validate_memmodel_limits(&start, &end);
      for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {

@@ -292,9 +279,19 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
  */
 static void __init memblocks_present(void)
 {
+     unsigned long __maybe_unused size, align;
      unsigned long start, end;
      int i, nid;

+#ifdef CONFIG_SPARSEMEM_EXTREME
+     size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
+     align = 1 << (INTERNODE_CACHE_SHIFT);
+     mem_section = memblock_alloc(size, align);
+     if (!mem_section)
+             panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
+                   __func__, size, align);
+#endif
+
      for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
              memory_present(nid, start, end);
 }
--

2.25.1

--
Sincerely yours,
Mike.