On (07/06/06 17:20), Andi Kleen didst pronounce:
>
> > Ok, while true, I'm not sure how it affects performance. The only "real"
> > value affected by present_pages is the number of patches that are
> > allocated in batches to the per-cpu allocator.
>
> It affects the low/high water marks in the VM zone balancer.
>
> Especially for the 16MB DMA zone it can make a difference if you
> account 4MB kernel in there or not.
>
Ok, the following patch will account for memmap usage on all
architectures. Optionally, a set_dma_reserve() may be called to account
for pages in ZONE_DMA that will never be usable. In this patch, only
x86_64 uses it.
After this patch is applied, the zone->present_pages figures are very
similar before and after arch-independent zone-sizing and the watermarks
are the same.
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/arch/x86_64/mm/init.c linux-2.6.17-rc6-mm1-106-account_kernel_mmap/arch/x86_64/mm/init.c
--- linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/arch/x86_64/mm/init.c 2006-06-08 13:45:07.000000000 +0100
+++ linux-2.6.17-rc6-mm1-106-account_kernel_mmap/arch/x86_64/mm/init.c 2006-06-09 09:18:55.000000000 +0100
@@ -660,8 +660,10 @@ void __init reserve_bootmem_generic(unsi
#else
reserve_bootmem(phys, len);
#endif
- if (phys+len <= MAX_DMA_PFN*PAGE_SIZE)
+ if (phys+len <= MAX_DMA_PFN*PAGE_SIZE) {
dma_reserve += len / PAGE_SIZE;
+ set_dma_reserve(dma_reserve);
+ }
}
int kern_addr_valid(unsigned long addr)
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/include/linux/mm.h linux-2.6.17-rc6-mm1-106-account_kernel_mmap/include/linux/mm.h
--- linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/include/linux/mm.h 2006-06-08 13:42:53.000000000 +0100
+++ linux-2.6.17-rc6-mm1-106-account_kernel_mmap/include/linux/mm.h 2006-06-09 09:18:55.000000000 +0100
@@ -969,6 +969,7 @@ extern void free_bootmem_with_active_reg
unsigned long max_low_pfn);
extern void sparse_memory_present_with_active_regions(int nid);
#endif /* CONFIG_ARCH_POPULATES_NODE_MAP */
+extern void set_dma_reserve(unsigned long new_dma_reserve);
extern void memmap_init_zone(unsigned long, int, unsigned long, unsigned long);
extern void setup_per_zone_pages_min(void);
extern void mem_init(void);
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/mm/page_alloc.c linux-2.6.17-rc6-mm1-106-account_kernel_mmap/mm/page_alloc.c
--- linux-2.6.17-rc6-mm1-105-ia64_use_init_nodes/mm/page_alloc.c 2006-06-08 13:42:53.000000000 +0100
+++ linux-2.6.17-rc6-mm1-106-account_kernel_mmap/mm/page_alloc.c 2006-06-09 09:18:55.000000000 +0100
@@ -88,6 +88,7 @@ int min_free_kbytes = 1024;
unsigned long __meminitdata nr_kernel_pages;
unsigned long __meminitdata nr_all_pages;
+unsigned long __initdata dma_reserve;
#ifdef CONFIG_ARCH_POPULATES_NODE_MAP
/*
@@ -2459,6 +2460,20 @@ unsigned long __init zone_absent_pages_i
arch_zone_lowest_possible_pfn[zone_type],
arch_zone_highest_possible_pfn[zone_type]);
}
+
+/* Return the zone index a PFN is in */
+int memmap_zone_idx(struct page *lmem_map)
+{
+ int i;
+ unsigned long phys_addr = virt_to_phys(lmem_map);
+ unsigned long pfn = phys_addr >> PAGE_SHIFT;
+
+ for (i = 0; i < MAX_NR_ZONES; i++)
+ if (pfn < arch_zone_highest_possible_pfn[i])
+ break;
+
+ return i;
+}
#else
static inline unsigned long zone_spanned_pages_in_node(int nid,
unsigned long zone_type,
@@ -2476,6 +2491,11 @@ static inline unsigned long zone_absent_
return zholes_size[zone_type];
}
+
+static inline int memmap_zone_idx(struct page *lmem_map)
+{
+ return MAX_NR_ZONES;
+}
#endif
static void __init calculate_node_totalpages(struct pglist_data *pgdat,
@@ -2499,6 +2519,58 @@ static void __init calculate_node_totalp
realtotalpages);
}
+#ifdef CONFIG_FLAT_NODE_MEM_MAP
+/* Account for mem_map for CONFIG_FLAT_NODE_MEM_MAP */
+unsigned long __meminit account_memmap(struct pglist_data *pgdat,
+ int zone_index)
+{
+ unsigned long pages = 0;
+ if (zone_index == memmap_zone_idx(pgdat->node_mem_map)) {
+ pages = pgdat->node_spanned_pages;
+ pages = (pages * sizeof(struct page)) >> PAGE_SHIFT;
+ printk(KERN_DEBUG "%lu pages used for memmap\n", pages);
+ }
+ return pages;
+}
+#else
+/* Account for mem_map for CONFIG_SPARSEMEM */
+unsigned long account_memmap(struct pglist_data *pgdat, int zone_index)
+{
+ unsigned long pages = 0;
+ unsigned long memmap_pfn;
+ struct page *memmap_addr;
+ int pnum;
+ unsigned long pgdat_startpfn, pgdat_endpfn;
+ struct mem_section *section;
+
+ pgdat_startpfn = pgdat->node_start_pfn;
+ pgdat_endpfn = pgdat_startpfn + pgdat->node_spanned_pages;
+
+ /* Go through valid sections looking for memmap */
+ for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
+ if (!valid_section_nr(pnum))
+ continue;
+
+ section = __nr_to_section(pnum);
+ if (!section_has_mem_map(section))
+ continue;
+
+ memmap_addr = __section_mem_map_addr(section);
+ memmap_pfn = (unsigned long)memmap_addr >> PAGE_SHIFT;
+
+ if (memmap_pfn < pgdat_startpfn || memmap_pfn >= pgdat_endpfn)
+ continue;
+
+ if (zone_index == memmap_zone_idx(memmap_addr))
+ pages += (PAGES_PER_SECTION * sizeof(struct page));
+ }
+
+ pages >>= PAGE_SHIFT;
+ printk(KERN_DEBUG "%lu pages used for SPARSE memmap\n", pages);
+ return pages;
+}
+#endif
+
/*
* Set up the zone data structures:
* - mark all pages reserved
@@ -2525,6 +2597,15 @@ static void __meminit free_area_init_cor
size = zone_spanned_pages_in_node(nid, j, zones_size);
realsize = size - zone_absent_pages_in_node(nid, j,
zholes_size);
+
+ realsize -= account_memmap(pgdat, j);
+ /* Account for reserved DMA pages */
+ if (j == ZONE_DMA && realsize > dma_reserve) {
+ realsize -= dma_reserve;
+ printk(KERN_DEBUG "%lu pages DMA reserved\n",
+ dma_reserve);
+ }
+
if (j < ZONE_HIGHMEM)
nr_kernel_pages += realsize;
nr_all_pages += realsize;
@@ -2849,6 +2930,21 @@ void __init free_area_init_nodes(unsigne
}
#endif /* CONFIG_ARCH_POPULATES_NODE_MAP */
+/**
+ * set_dma_reserve - Account the specified number of pages reserved in ZONE_DMA
+ * @new_dma_reserve - The number of pages to mark reserved
+ *
+ * The per-cpu batchsize and zone watermarks are determined by present_pages.
+ * In the DMA zone, a significant percentage may be consumed by kernel image
+ * and other unfreeable allocations which can skew the watermarks badly. This
+ * function may optionally be used to account for unfreeable pages in
+ * ZONE_DMA. The effect will be lower watermarks and smaller per-cpu batchsize
+ */
+void __init set_dma_reserve(unsigned long new_dma_reserve)
+{
+ dma_reserve = new_dma_reserve;
+}
+
#ifndef CONFIG_NEED_MULTIPLE_NODES
static bootmem_data_t contig_bootmem_data;
struct pglist_data contig_page_data = { .bdata = &contig_bootmem_data };
--
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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