Hi Robin,
On 07/12/2013 10:03 AM, Robin Holt wrote:
Currently, when free_all_bootmem() calls __free_pages_memory(), the
number of contiguous pages that __free_pages_memory() passes to the
buddy allocator is limited to BITS_PER_LONG.  In order to be able to

I fail to understand this. Why the original page number is BITS_PER_LONG?

free only the first page of a 2MiB chunk, we need that to be increased
to PTRS_PER_PMD.

Signed-off-by: Robin Holt <h...@sgi.com>
Signed-off-by: Nate Zimmer <nzim...@sgi.com>
To: "H. Peter Anvin" <h...@zytor.com>
To: Ingo Molnar <mi...@kernel.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Cc: Linux MM <linux...@kvack.org>
Cc: Rob Landley <r...@landley.net>
Cc: Mike Travis <tra...@sgi.com>
Cc: Daniel J Blueman <dan...@numascale-asia.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Greg KH <gre...@linuxfoundation.org>
Cc: Yinghai Lu <ying...@kernel.org>
Cc: Mel Gorman <mgor...@suse.de>
---
  mm/nobootmem.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/nobootmem.c b/mm/nobootmem.c
index bdd3fa2..3b512ca 100644
--- a/mm/nobootmem.c
+++ b/mm/nobootmem.c
@@ -83,10 +83,10 @@ void __init free_bootmem_late(unsigned long addr, unsigned 
long size)
  static void __init __free_pages_memory(unsigned long start, unsigned long end)
  {
        unsigned long i, start_aligned, end_aligned;
-       int order = ilog2(BITS_PER_LONG);
+       int order = ilog2(max(BITS_PER_LONG, PTRS_PER_PMD));
- start_aligned = (start + (BITS_PER_LONG - 1)) & ~(BITS_PER_LONG - 1);
-       end_aligned = end & ~(BITS_PER_LONG - 1);
+       start_aligned = (start + ((1UL << order) - 1)) & ~((1UL << order) - 1);
+       end_aligned = end & ~((1UL << order) - 1);
if (end_aligned <= start_aligned) {
                for (i = start; i < end; i++)
@@ -98,7 +98,7 @@ static void __init __free_pages_memory(unsigned long start, 
unsigned long end)
        for (i = start; i < start_aligned; i++)
                __free_pages_bootmem(pfn_to_page(i), 0);
- for (i = start_aligned; i < end_aligned; i += BITS_PER_LONG)
+       for (i = start_aligned; i < end_aligned; i += 1 << order)
                __free_pages_bootmem(pfn_to_page(i), order);
for (i = end_aligned; i < end; i++)

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