+ page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch added to -mm tree

+ page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch added to -mm tree

[akpm]

The patch titled
     page_cgroup: reduce allocation overhead for page_cgroup array for CONFIG_SPARSEMEM
has been added to the -mm tree.  Its filename is
     page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch

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*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: page_cgroup: reduce allocation overhead for page_cgroup array for CONFIG_SPARSEMEM
From: Michal Hocko <mhocko@suse.cz>

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@suse.cz>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_cgroup.c |   56 +++++++++++++++++++++++++++------------------
 1 file changed, 34 insertions(+), 22 deletions(-)

diff -puN mm/page_cgroup.c~page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem mm/page_cgroup.c
--- a/mm/page_cgroup.c~page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem
+++ a/mm/page_cgroup.c
@@ -130,7 +130,36 @@ struct page *lookup_cgroup_page(struct p
 	return page;
 }
 
-/* __alloc_bootmem...() is protected by !slab_available() */
+static void *__init_refok alloc_page_cgroup(size_t size, int nid)
+{
+	void *addr = NULL;
+
+	addr = alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
+	if (addr)
+		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 page_cgroup *base, *pc;
@@ -147,17 +176,8 @@ static int __init_refok init_section_pag
 
 	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);
-	}
+	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,
@@ -189,16 +209,8 @@ void __free_page_cgroup(unsigned long pf
 	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,
_

Patches currently in -mm which might be from mhocko@suse.cz are

memsw-remove-noswapaccount-kernel-parameter.patch
page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch

Re: + page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch added to -mm tree

[Johannes Weiner]

From: Johannes Weiner <hannes@cmpxchg.org>
Subject: [patch] mm: do not define unused free_page_cgroup without memory hotplug

Without memory hotplug configured in, the page cgroup array is never
actually freed again:

mm/page_cgroup.c:149:13: warning: a??free_page_cgroupa?? defined but not used

Wrap the definition in ifdefs.  Rather than moving it into an existing
ifdef section, to keep it close to its allocation counterpart.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/page_cgroup.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 885b2ac..a12cc3f 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -146,6 +146,7 @@ static void *__init_refok alloc_page_cgroup(size_t size, int nid)
 	return addr;
 }
 
+#ifdef CONFIG_MEMORY_HOTPLUG
 static void free_page_cgroup(void *addr)
 {
 	if (is_vmalloc_addr(addr)) {
@@ -159,6 +160,7 @@ static void free_page_cgroup(void *addr)
 		free_pages_exact(addr, table_size);
 	}
 }
+#endif
 
 static int __init_refok init_section_page_cgroup(unsigned long pfn)
 {
-- 
1.7.4

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Re: + page_cgroup-reduce-allocation-overhead-for-page_cgroup-array-for-config_sparsemem.patch added to -mm tree

[Michal Hocko]

On Tue 22-03-11 10:24:21, Johannes Weiner wrote:
> From: Johannes Weiner <hannes@cmpxchg.org>
> Subject: [patch] mm: do not define unused free_page_cgroup without memory hotplug
> 
> Without memory hotplug configured in, the page cgroup array is never
> actually freed again:
> 
> mm/page_cgroup.c:149:13: warning: ???free_page_cgroup??? defined but not used
> 
> Wrap the definition in ifdefs.  Rather than moving it into an existing
> ifdef section, to keep it close to its allocation counterpart.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Makes perfect sense. Thanks!

Ackedy-by: Michal Hocko <mhocko@suse.cz>

> ---
>  mm/page_cgroup.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index 885b2ac..a12cc3f 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -146,6 +146,7 @@ static void *__init_refok alloc_page_cgroup(size_t size, int nid)
>  	return addr;
>  }
>  
> +#ifdef CONFIG_MEMORY_HOTPLUG
>  static void free_page_cgroup(void *addr)
>  {
>  	if (is_vmalloc_addr(addr)) {
> @@ -159,6 +160,7 @@ static void free_page_cgroup(void *addr)
>  		free_pages_exact(addr, table_size);
>  	}
>  }
> +#endif
>  
>  static int __init_refok init_section_page_cgroup(unsigned long pfn)
>  {
> -- 
> 1.7.4

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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