On Mon, 28 Feb 2011 11:09:20 +0100 Michal Hocko <mhocko@xxxxxxx> wrote: > 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. > > ... > > @@ -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, This conflicts with memcg-remove-direct-page_cgroup-to-page-pointer.patch, which did static int __init_refok init_section_page_cgroup(unsigned long pfn) { - struct mem_section *section = __pfn_to_section(pfn); struct page_cgroup *base, *pc; + struct mem_section *section; unsigned long table_size; + unsigned long nr; 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); - } - /* - * The value stored in section->page_cgroup is (base - pfn) - * and it does not point to the memory block allocated above, - * causing kmemleak false positives. - */ - kmemleak_not_leak(base); + nr = pfn_to_section_nr(pfn); + section = __nr_to_section(nr); + + if (section->page_cgroup) + return 0; + + 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); -- 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>