Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1037b83bd04e31449dc9323f1e8ddada4264ef66
Commit:     1037b83bd04e31449dc9323f1e8ddada4264ef66
Parent:     b92151bab91ef906378d3e0e7128d55dd641e966
Author:     Eric Dumazet <[EMAIL PROTECTED]>
AuthorDate: Sun Jul 15 23:38:05 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Mon Jul 16 09:05:35 2007 -0700

    MM: alloc_large_system_hash() can free some memory for non power-of-two 
bucketsize
    
    alloc_large_system_hash() is called at boot time to allocate space for
    several large hash tables.
    
    Lately, TCP hash table was changed and its bucketsize is not a power-of-two
    anymore.
    
    On most setups, alloc_large_system_hash() allocates one big page (order >
    0) with __get_free_pages(GFP_ATOMIC, order).  This single high_order page
    has a power-of-two size, bigger than the needed size.
    
    We can free all pages that wont be used by the hash table.
    
    On a 1GB i386 machine, this patch saves 128 KB of LOWMEM memory.
    
    TCP established hash table entries: 32768 (order: 6, 393216 bytes)
    
    Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 mm/page_alloc.c |   15 +++++++++++++++
 1 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 092b2d8..8dadda6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3584,6 +3584,21 @@ void *__init alloc_large_system_hash(const char 
*tablename,
                        for (order = 0; ((1UL << order) << PAGE_SHIFT) < size; 
order++)
                                ;
                        table = (void*) __get_free_pages(GFP_ATOMIC, order);
+                       /*
+                        * If bucketsize is not a power-of-two, we may free
+                        * some pages at the end of hash table.
+                        */
+                       if (table) {
+                               unsigned long alloc_end = (unsigned long)table +
+                                               (PAGE_SIZE << order);
+                               unsigned long used = (unsigned long)table +
+                                               PAGE_ALIGN(size);
+                               split_page(virt_to_page(table), order);
+                               while (used < alloc_end) {
+                                       free_page(used);
+                                       used += PAGE_SIZE;
+                               }
+                       }
                }
        } while (!table && size > PAGE_SIZE && --log2qty);
 
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