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Date: Fri, 26 Sep 2008 10:00:22 +0900
From: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: nishimura@....nes.nec.co.jp,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
"xemul@...nvz.org" <xemul@...nvz.org>,
Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Dave Hansen <haveblue@...ibm.com>, ryov@...inux.co.jp
Subject: Re: [PATCH 9/12] memcg allocate all page_cgroup at boot
On Thu, 25 Sep 2008 15:32:06 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> Allocate all page_cgroup at boot and remove page_cgroup poitner
> from struct page. This patch adds an interface as
>
> struct page_cgroup *lookup_page_cgroup(struct page*)
>
> All FLATMEM/DISCONTIGMEM/SPARSEMEM and MEMORY_HOTPLUG is supported.
>
> Remove page_cgroup pointer reduces the amount of memory by
> - 4 bytes per PAGE_SIZE.
> - 8 bytes per PAGE_SIZE
> if memory controller is disabled. (even if configured.)
> meta data usage of this is no problem in FLATMEM/DISCONTIGMEM.
> On SPARSEMEM, this makes mem_section[] size twice.
>
> On usual 8GB x86-32 server, this saves 8MB of NORMAL_ZONE memory.
> On my x86-64 server with 48GB of memory, this saves 96MB of memory.
> (and uses xx kbytes for mem_section.)
> I think this reduction makes sense.
>
> By pre-allocation, kmalloc/kfree in charge/uncharge are removed.
> This means
> - we're not necessary to be afraid of kmalloc faiulre.
> (this can happen because of gfp_mask type.)
> - we can avoid calling kmalloc/kfree.
> - we can avoid allocating tons of small objects which can be fragmented.
> - we can know what amount of memory will be used for this extra-lru handling.
>
> I added printk message as
>
> "allocated %ld bytes of page_cgroup"
> "please try cgroup_disable=memory option if you don't want"
>
> maybe enough informative for users.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> include/linux/memcontrol.h | 11 -
> include/linux/mm_types.h | 4
> include/linux/mmzone.h | 9 +
> include/linux/page_cgroup.h | 90 +++++++++++++++
> mm/Makefile | 2
> mm/memcontrol.c | 258 ++++++++++++--------------------------------
> mm/page_alloc.c | 12 --
> mm/page_cgroup.c | 253 +++++++++++++++++++++++++++++++++++++++++++
> 8 files changed, 431 insertions(+), 208 deletions(-)
>
> Index: mmotm-2.6.27-rc7+/mm/page_cgroup.c
> ===================================================================
> --- /dev/null
> +++ mmotm-2.6.27-rc7+/mm/page_cgroup.c
> @@ -0,0 +1,253 @@
> +#include <linux/mm.h>
> +#include <linux/mmzone.h>
> +#include <linux/bootmem.h>
> +#include <linux/bit_spinlock.h>
> +#include <linux/page_cgroup.h>
> +#include <linux/hash.h>
> +#include <linux/memory.h>
> +
> +static void __meminit
> +__init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
> +{
> + pc->flags = 0;
> + pc->mem_cgroup = NULL;
> + pc->page = pfn_to_page(pfn);
> +}
> +static unsigned long total_usage = 0;
> +
> +#ifdef CONFIG_FLAT_NODE_MEM_MAP
> +
> +
> +void __init pgdat_page_cgroup_init(struct pglist_data *pgdat)
> +{
> + pgdat->node_page_cgroup = NULL;
> +}
> +
> +struct page_cgroup *lookup_page_cgroup(struct page *page)
> +{
> + unsigned long pfn = page_to_pfn(page);
> + unsigned long offset;
> + struct page_cgroup *base;
> +
> + base = NODE_DATA(page_to_nid(nid))->node_page_cgroup;
page_to_nid(page) :)
> + if (unlikely(!base))
> + return NULL;
> +
> + offset = pfn - NODE_DATA(page_to_nid(page))->node_start_pfn;
> + return base + offset;
> +}
> +
> +static int __init alloc_node_page_cgroup(int nid)
> +{
> + struct page_cgroup *base, *pc;
> + unsigned long table_size;
> + unsigned long start_pfn, nr_pages, index;
> +
> + start_pfn = NODE_DATA(nid)->node_start_pfn;
> + nr_pages = NODE_DATA(nid)->node_spanned_pages;
> +
> + table_size = sizeof(struct page_cgroup) * nr_pages;
> +
> + base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),
> + table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
> + if (!base)
> + return -ENOMEM;
> + for (index = 0; index < nr_pages; index++) {
> + pc = base + index;
> + __init_page_cgroup(pc, start_pfn + index);
> + }
> + NODE_DATA(nid)->node_page_cgroup = base;
> + total_usage += table_size;
> + return 0;
> +}
> +
> +void __init free_node_page_cgroup(int nid)
> +{
> + unsigned long table_size;
> + unsigned long nr_pages;
> + struct page_cgroup *base;
> +
> + base = NODE_DATA(nid)->node_page_cgroup;
> + if (!base)
> + return;
> + nr_pages = NODE_DATA(nid)->node_spanned_pages;
> +
> + table_size = sizeof(struct page_cgroup) * nr_pages;
> +
> + free_bootmem_node(NODE_DATA(nid),
> + (unsigned long)base, table_size);
> + NODE_DATA(nid)->node_page_cgroup = NULL;
> +}
> +
Hmm, who uses this function?
(snip)
> @@ -812,49 +708,41 @@ __mem_cgroup_uncharge_common(struct page
>
> if (mem_cgroup_subsys.disabled)
> return;
> + /* check the condition we can know from page */
>
> - /*
> - * Check if our page_cgroup is valid
> - */
> - lock_page_cgroup(page);
> - pc = page_get_page_cgroup(page);
> - if (unlikely(!pc))
> - goto unlock;
> -
> - VM_BUG_ON(pc->page != page);
> + pc = lookup_page_cgroup(page);
> + if (unlikely(!pc || !PageCgroupUsed(pc)))
> + return;
> + preempt_disable();
> + lock_page_cgroup(pc);
> + if (unlikely(page_mapped(page))) {
> + unlock_page_cgroup(pc);
> + preempt_enable();
> + return;
> + }
Just for clarification, in what sequence will the page be mapped here?
mem_cgroup_uncharge_page checks whether the page is mapped.
> + ClearPageCgroupUsed(pc);
> + unlock_page_cgroup(pc);
>
> - if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
> - && ((PageCgroupCache(pc) || page_mapped(page))))
> - goto unlock;
> -retry:
> mem = pc->mem_cgroup;
> mz = page_cgroup_zoneinfo(pc);
> +
> spin_lock_irqsave(&mz->lru_lock, flags);
> - if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED &&
> - unlikely(mem != pc->mem_cgroup)) {
> - /* MAPPED account can be done without lock_page().
> - Check race with mem_cgroup_move_account() */
> - spin_unlock_irqrestore(&mz->lru_lock, flags);
> - goto retry;
> - }
By these changes, ctype becomes unnecessary so it can be removed.
> __mem_cgroup_remove_list(mz, pc);
> spin_unlock_irqrestore(&mz->lru_lock, flags);
> -
> - page_assign_page_cgroup(page, NULL);
> - unlock_page_cgroup(page);
> -
> -
> - res_counter_uncharge(&mem->res, PAGE_SIZE);
> + pc->mem_cgroup = NULL;
> css_put(&mem->css);
> + preempt_enable();
> + res_counter_uncharge(&mem->res, PAGE_SIZE);
>
> - kmem_cache_free(page_cgroup_cache, pc);
> return;
> -unlock:
> - unlock_page_cgroup(page);
> }
>
Thanks,
Daisuke Nishimura.
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