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Re: [PATCH] do not count pages in holes with sparsemem

To: "Atsushi Nemoto" <anemo@mba.ocn.ne.jp>
Subject: Re: [PATCH] do not count pages in holes with sparsemem
From: "Franck Bui-Huu" <vagabon.xyz@gmail.com>
Date: Mon, 10 Jul 2006 13:34:06 +0200
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
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2006/7/6, Atsushi Nemoto <anemo@mba.ocn.ne.jp>:

Sure.  Then this can be a final proposal?


could you put the diffstat next time ?


With some memory model other than FLATMEM, the single node can
contains some holes so there might be many invalid pages.  For
example, with two 256M memory and one 256M hole, some variables
(num_physpage, totalpages, nr_kernel_pages, nr_all_pages, etc.) will
indicate that there are 768MB on this system.  This is not desired
because, for example, alloc_large_system_hash() allocates too many
entries.

Use free_area_init_node() with counted zholes_size[] instead of
free_area_init().

For num_physpages, use number of ram pages instead of max_low_pfn.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 802bdd3..c52497b 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -139,10 +139,36 @@ #endif /* CONFIG_HIGHMEM */
 #ifndef CONFIG_NEED_MULTIPLE_NODES
 extern void pagetable_init(void);

+static int __init page_is_ram(unsigned long pagenr)
+{
+       int i;
+
+       for (i = 0; i < boot_mem_map.nr_map; i++) {
+               unsigned long addr, end;
+
+               if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
+                       /* not usable memory */
+                       continue;
+
+               addr = PFN_UP(boot_mem_map.map[i].addr);
+               end = PFN_DOWN(boot_mem_map.map[i].addr +
+                              boot_mem_map.map[i].size);
+
+               if (pagenr >= addr && pagenr < end)
+                       return 1;
+       }
+
+       return 0;
+}
+
 void __init paging_init(void)
 {
-       unsigned long zones_size[MAX_NR_ZONES] = {0, 0, 0};
+       unsigned long zones_size[] = { [0 ... MAX_NR_ZONES - 1] = 0 };
        unsigned long max_dma, high, low;
+#ifndef CONFIG_FLATMEM
+       unsigned long zholes_size[] = { [0 ... MAX_NR_ZONES - 1] = 0 };
+       unsigned long i, j, pfn;
+#endif

        pagetable_init();

@@ -174,29 +200,16 @@ #ifdef CONFIG_HIGHMEM
                zones_size[ZONE_HIGHMEM] = high - low;
 #endif

+#ifdef CONFIG_FLATMEM
        free_area_init(zones_size);
-}
-
-static inline int page_is_ram(unsigned long pagenr)
-{
-       int i;
-
-       for (i = 0; i < boot_mem_map.nr_map; i++) {
-               unsigned long addr, end;
-
-               if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
-                       /* not usable memory */
-                       continue;
-
-               addr = PFN_UP(boot_mem_map.map[i].addr);
-               end = PFN_DOWN(boot_mem_map.map[i].addr +
-                              boot_mem_map.map[i].size);
-
-               if (pagenr >= addr && pagenr < end)
-                       return 1;
-       }
-
-       return 0;
+#else
+       pfn = 0;
+       for (i = 0; i < MAX_NR_ZONES; i++)
+               for (j = 0; j < zones_size[i]; j++, pfn++)
+                       if (!page_is_ram(pfn))

can we use pfn_valid() instead of page_is_ram() ? bootmem_init() and
sparse_init() have already been called so pfn_valid() should be safe
here....

+                               zholes_size[i]++;
+       free_area_init_node(0, NODE_DATA(0), zones_size, 0, zholes_size);
+#endif
 }

 static struct kcore_list kcore_mem, kcore_vmalloc;
@@ -213,9 +226,9 @@ #ifdef CONFIG_HIGHMEM
 #ifdef CONFIG_DISCONTIGMEM
 #error "CONFIG_HIGHMEM and CONFIG_DISCONTIGMEM dont work together yet"
 #endif
-       max_mapnr = num_physpages = highend_pfn;
+       max_mapnr = highend_pfn;
 #else
-       max_mapnr = num_physpages = max_low_pfn;
+       max_mapnr = max_low_pfn;

this is not always true, specially if FLATMEM set and your physical mem
do not start at 0.

 #endif
        high_memory = (void *) __va(max_low_pfn << PAGE_SHIFT);

@@ -229,6 +242,7 @@ #endif

in this loop can we use pfn_valid() instead of page_is_ram() ? Therefore
we could get rid of the latter macro ?

                        if (PageReserved(pfn_to_page(tmp)))
                                reservedpages++;
                }
+       num_physpages = ram;

 #ifdef CONFIG_HIGHMEM
        for (tmp = highstart_pfn; tmp < highend_pfn; tmp++) {
@@ -247,6 +261,7 @@ #endif
                totalhigh_pages++;
        }
        totalram_pages += totalhigh_pages;
+       num_physpages += totalhigh_pages;
 #endif

        codesize =  (unsigned long) &_etext - (unsigned long) &_text;


--
              Franck

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