Hi Andrew, could you consider the patch bellow, please? The patch was discussed at https://lkml.org/lkml/2011/2/23/232 --- >From 7e5b1e7043605891dacd9e32f19985bc675292f5 Mon Sep 17 00:00:00 2001 From: Michal Hocko <mhocko@xxxxxxx> Date: Thu, 24 Feb 2011 11:25:44 +0100 Subject: [PATCH 1/2] page_cgroup: Reduce allocation overhead for page_cgroup array for CONFIG_SPARSEMEM Currently we are allocating a single page_cgroup array per memory section (stored in mem_section->base) when CONFIG_SPARSEMEM is selected. This is correct but memory inefficient solution because the allocated memory (unless we fall back to vmalloc) is not kmalloc friendly: - 32b - 16384 entries (20B per entry) fit into 327680B so the 524288B slab cache is used - 32b with PAE - 131072 entries with 2621440B fit into 4194304B - 64b - 32768 entries (40B per entry) fit into 2097152 cache This is ~37% wasted space per memory section and it sumps up for the whole memory. On a x86_64 machine it is something like 6MB per 1GB of RAM. We can reduce the internal fragmentation by using alloc_pages_exact which allocates PAGE_SIZE aligned blocks so we will get down to <4kB wasted memory per section which is much better. We still need a fallback to vmalloc because we have no guarantees that we will have a continuous memory of that size (order-10) later on during the hotplug events. Signed-off-by: Michal Hocko <mhocko@xxxxxxx> CC: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> --- mm/page_cgroup.c | 54 +++++++++++++++++++++++++++++++----------------------- 1 files changed, 31 insertions(+), 23 deletions(-) diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c index 5bffada..eae3cd2 100644 --- a/mm/page_cgroup.c +++ b/mm/page_cgroup.c @@ -105,7 +105,33 @@ struct page_cgroup *lookup_page_cgroup(struct page *page) return section->page_cgroup + pfn; } -/* __alloc_bootmem...() is protected by !slab_available() */ +static void *__init_refok alloc_page_cgroup(size_t size, int nid) +{ + void *addr = NULL; + if((addr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN))) + return addr; + + if (node_state(nid, N_HIGH_MEMORY)) + addr = vmalloc_node(size, nid); + else + addr = vmalloc(size); + + return addr; +} + +static void free_page_cgroup(void *addr) +{ + if (is_vmalloc_addr(addr)) { + vfree(addr); + } else { + struct page *page = virt_to_page(addr); + if (!PageReserved(page)) { /* Is bootmem ? */ + size_t table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION; + free_pages_exact(addr, table_size); + } + } +} + static int __init_refok init_section_page_cgroup(unsigned long pfn) { struct mem_section *section = __pfn_to_section(pfn); @@ -114,19 +140,9 @@ static int __init_refok init_section_page_cgroup(unsigned long pfn) int nid, index; if (!section->page_cgroup) { - nid = page_to_nid(pfn_to_page(pfn)); table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION; - VM_BUG_ON(!slab_is_available()); - if (node_state(nid, N_HIGH_MEMORY)) { - base = kmalloc_node(table_size, - GFP_KERNEL | __GFP_NOWARN, nid); - if (!base) - base = vmalloc_node(table_size, nid); - } else { - base = kmalloc(table_size, GFP_KERNEL | __GFP_NOWARN); - if (!base) - base = vmalloc(table_size); - } + nid = page_to_nid(pfn_to_page(pfn)); + base = alloc_page_cgroup(table_size, nid); /* * The value stored in section->page_cgroup is (base - pfn) * and it does not point to the memory block allocated above, @@ -170,16 +186,8 @@ void __free_page_cgroup(unsigned long pfn) if (!ms || !ms->page_cgroup) return; base = ms->page_cgroup + pfn; - if (is_vmalloc_addr(base)) { - vfree(base); - ms->page_cgroup = NULL; - } else { - struct page *page = virt_to_page(base); - if (!PageReserved(page)) { /* Is bootmem ? */ - kfree(base); - ms->page_cgroup = NULL; - } - } + free_page_cgroup(base); + ms->page_cgroup = NULL; } int __meminit online_page_cgroup(unsigned long start_pfn, -- 1.7.2.3 -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>