Re: [PATCH] Apply memory policies to top two highest zones when highest zone is ZONE_MOVABLE

From: Mel Gorman
Date: Sat Aug 04 2007 - 12:39:34 EST

On (04/08/07 10:51), Andi Kleen didst pronounce:
>
> > It only affects hot paths in the NUMA case so non-NUMA users will not care.
>
> For x86-64 most distribution kernels are NUMA these days.
>
> > For NUMA users, I have posted patches that eliminate multiple zonelists
> > altogether which will reduce cache footprint (something like 7K per node on
> > x86_64)
>
> How do you get to 7k? We got worst case 3 zones node (normally less);
> that's three pointers per GFP level.
>

The zonelists are pretty big. On a 4 node x86_64 machine (elm3b6 from tko),
the size of pg_data_t goes from 13632 bytes to 5824 (almost 8k in fact)
when only one zonelists is used.

> > and make things like MPOL_BIND behave in a consistent manner. That
> > would cost on CPU but save on cache which would (hopefully) result in a net
> > gain in most cases.
>
> That might be a good tradeoff, but without seeing the patch
> the 7k number sounds very dubious.
>

Proof-of-concept patch is below. It's not suitable for merging and I was
getting the policy issue resolved first before spending more time on it. The
patch was a big too heavy to call a fix for a bug.

> > I would like to go with this patch for now just for policies but for
> > 2.6.23, we could leave it as "policies only apply to ZONE_MOVABLE when it
> > is used" if you really insisted on it. It's less than ideal though for
> > sure.
>
> Or disable ZONE_MOVABLE. It seems to be clearly not well thought
> out well yet.

The zone is disabled by default. When enabled, the policies are only applied
to it which is expected, but not desirable which is why I wanted to apply
policies to the two highest zones when the highest was ZONE_MOVABLE.

>Perhaps make it dependent on !CONFIG_NUMA.
>

That would make no sense. The systems that will be using hugepages and
looking to resize their pool will often be NUMA machines and you state
that most x86_64 distros will have NUMA enabled.

This is the prototype patch for removing multiple zonelists altogether.
It would also act as a fix for the
policies-only-applying-to-ZONE_MOVABLE problem. You may not that where
the filtering takes place in __alloc_pages() is in the same place as
with the patch to fix policies so there is a logical progression from
bug fix now to something with wider usefulness later.

diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index e724b36..4d417c4 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -602,12 +602,15 @@ void show_mem(void)
int i, j, k;

for (i = 0; i < npmem_ranges; i++) {
+ zl = &NODE_DATA(i)->node_zonelist;
for (j = 0; j < MAX_NR_ZONES; j++) {
- zl = NODE_DATA(i)->node_zonelists + j;

printk("Zone list for zone %d on node %d: ", j, i);
- for (k = 0; zl->zones[k] != NULL; k++)
+ for (k = 0; zl->zones[k] != NULL; k++) {
+ if (should_filter_zone(zl->zones[k]), j)
+ continue;
printk("[%ld/%s] ", zone_to_nid(zl->zones[k]), zl->zones[k]->name);
+ }
printk("\n");
}
}
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 39cc318..b56d17f 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -270,7 +270,7 @@ static struct sysrq_key_op sysrq_term_op = {

static void moom_callback(struct work_struct *ignored)
{
- out_of_memory(&NODE_DATA(0)->node_zonelists[ZONE_NORMAL],
+ out_of_memory(&NODE_DATA(0)->node_zonelist,
GFP_KERNEL, 0);
}

diff --git a/fs/buffer.c b/fs/buffer.c
index 0e5ec37..8e9bbef 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -354,7 +354,7 @@ static void free_more_memory(void)
yield();

for_each_online_pgdat(pgdat) {
- zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
+ zones = pgdat->node_zonelist.zones;
if (*zones)
try_to_free_pages(zones, 0, GFP_NOFS);
}
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index bc68dd9..f2a597e 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -116,6 +116,13 @@ static inline enum zone_type gfp_zone(gfp_t flags)
return ZONE_NORMAL;
}

+static inline int should_filter_zone(struct zone *zone, int highest_zoneidx)
+{
+ if (zone_idx(zone) > highest_zoneidx)
+ return 1;
+ return 0;
+}
+
/*
* There is only one page-allocator function, and two main namespaces to
* it. The alloc_page*() variants return 'struct page *' and as such
@@ -151,8 +158,7 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
if (nid < 0)
nid = numa_node_id();

- return __alloc_pages(gfp_mask, order,
- NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_mask));
+ return __alloc_pages(gfp_mask, order, &NODE_DATA(nid)->node_zonelist);
}

#ifdef CONFIG_NUMA
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index e147cf5..83e5256 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -166,7 +166,7 @@ extern enum zone_type policy_zone;

static inline void check_highest_zone(enum zone_type k)
{
- if (k > policy_zone)
+ if (k > policy_zone && k != ZONE_MOVABLE)
policy_zone = k;
}

@@ -258,7 +258,7 @@ static inline void mpol_fix_fork_child_flag(struct task_struct *p)
static inline struct zonelist *huge_zonelist(struct vm_area_struct *vma,
unsigned long addr, gfp_t gfp_flags)
{
- return NODE_DATA(0)->node_zonelists + gfp_zone(gfp_flags);
+ return &NODE_DATA(0)->node_zonelist;
}

static inline int do_migrate_pages(struct mm_struct *mm,
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3ea68cd..d2fe32e 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -201,6 +201,7 @@ struct zone {
*/
unsigned long lowmem_reserve[MAX_NR_ZONES];

+ int zone_idx;
#ifdef CONFIG_NUMA
int node;
/*
@@ -437,7 +438,7 @@ extern struct page *mem_map;
struct bootmem_data;
typedef struct pglist_data {
struct zone node_zones[MAX_NR_ZONES];
- struct zonelist node_zonelists[MAX_NR_ZONES];
+ struct zonelist node_zonelist;
int nr_zones;
#ifdef CONFIG_FLAT_NODE_MEM_MAP
struct page *node_mem_map;
@@ -501,7 +502,7 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
/*
* zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
*/
-#define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
+#define zone_idx(zone) ((zone)->zone_idx)

static inline int populated_zone(struct zone *zone)
{
@@ -543,7 +544,7 @@ static inline int is_normal_idx(enum zone_type idx)
static inline int is_highmem(struct zone *zone)
{
#ifdef CONFIG_HIGHMEM
- int zone_idx = zone - zone->zone_pgdat->node_zones;
+ int zone_idx = zone_idx(zone);
return zone_idx == ZONE_HIGHMEM ||
(zone_idx == ZONE_MOVABLE && zone_movable_is_highmem());
#else
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 71b84b4..8b16ca3 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -149,7 +149,7 @@ static struct zonelist *bind_zonelist(nodemask_t *nodes)
lower zones etc. Avoid empty zones because the memory allocator
doesn't like them. If you implement node hot removal you
have to fix that. */
- k = policy_zone;
+ k = MAX_NR_ZONES - 1;
while (1) {
for_each_node_mask(nd, *nodes) {
struct zone *z = &NODE_DATA(nd)->node_zones[k];
@@ -1116,7 +1116,7 @@ static struct zonelist *zonelist_policy(gfp_t gfp, struct mempolicy *policy)
nd = 0;
BUG();
}
- return NODE_DATA(nd)->node_zonelists + gfp_zone(gfp);
+ return &NODE_DATA(nd)->node_zonelist;
}

/* Do dynamic interleaving for a process */
@@ -1212,7 +1212,7 @@ struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr,
unsigned nid;

nid = interleave_nid(pol, vma, addr, HPAGE_SHIFT);
- return NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_flags);
+ return &NODE_DATA(nid)->node_zonelist;
}
return zonelist_policy(GFP_HIGHUSER, pol);
}
@@ -1226,7 +1226,7 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
struct zonelist *zl;
struct page *page;

- zl = NODE_DATA(nid)->node_zonelists + gfp_zone(gfp);
+ zl = &NODE_DATA(nid)->node_zonelist;
page = __alloc_pages(gfp, order, zl);
if (page && page_zone(page) == zl->zones[0])
inc_zone_page_state(page, NUMA_INTERLEAVE_HIT);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f9b82ad..1cca18e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -179,6 +179,7 @@ static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
struct zone **z;
nodemask_t nodes;
int node;
+ enum zone_type highest_zoneidx = gfp_zone(gfp_mask);

nodes_clear(nodes);
/* node has memory ? */
@@ -186,11 +187,15 @@ static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
if (NODE_DATA(node)->node_present_pages)
node_set(node, nodes);

- for (z = zonelist->zones; *z; z++)
+ for (z = zonelist->zones; *z; z++) {
+
+ if (should_filter_zone(*z, highest_zoneidx))
+ continue;
if (cpuset_zone_allowed_softwall(*z, gfp_mask))
node_clear(zone_to_nid(*z), nodes);
else
return CONSTRAINT_CPUSET;
+ }

if (!nodes_empty(nodes))
return CONSTRAINT_MEMORY_POLICY;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3da85b8..190994d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1157,6 +1157,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order,
nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
int zlc_active = 0; /* set if using zonelist_cache */
int did_zlc_setup = 0; /* just call zlc_setup() one time */
+ enum zone_type highest_zoneidx = gfp_zone(gfp_mask);

zonelist_scan:
/*
@@ -1166,6 +1167,9 @@ zonelist_scan:
z = zonelist->zones;

do {
+ if (should_filter_zone(*z, highest_zoneidx))
+ continue;
+
if (NUMA_BUILD && zlc_active &&
!zlc_zone_worth_trying(zonelist, z, allowednodes))
continue;
@@ -1460,11 +1464,11 @@ static unsigned int nr_free_zone_pages(int offset)
pg_data_t *pgdat = NODE_DATA(numa_node_id());
unsigned int sum = 0;

- struct zonelist *zonelist = pgdat->node_zonelists + offset;
- struct zone **zonep = zonelist->zones;
- struct zone *zone;
+ struct zone **zonep = pgdat->node_zonelist.zones;
+ struct zone *zone = *zonep;

- for (zone = *zonep++; zone; zone = *zonep++) {
+ for (zone = *zonep++; zone && zone_idx(zone) > offset; zone = *zonep++);
+ for (; zone; zone = *zonep++) {
unsigned long size = zone->present_pages;
unsigned long high = zone->pages_high;
if (size > high)
@@ -1823,17 +1827,14 @@ static int find_next_best_node(int node, nodemask_t *used_node_mask)
*/
static void build_zonelists_in_node_order(pg_data_t *pgdat, int node)
{
- enum zone_type i;
int j;
struct zonelist *zonelist;

- for (i = 0; i < MAX_NR_ZONES; i++) {
- zonelist = pgdat->node_zonelists + i;
- for (j = 0; zonelist->zones[j] != NULL; j++)
- ;
- j = build_zonelists_node(NODE_DATA(node), zonelist, j, i);
- zonelist->zones[j] = NULL;
- }
+ zonelist = &pgdat->node_zonelist;
+ for (j = 0; zonelist->zones[j] != NULL; j++)
+ ;
+ j = build_zonelists_node(NODE_DATA(node), zonelist, j, MAX_NR_ZONES-1);
+ zonelist->zones[j] = NULL;
}

/*
@@ -1846,27 +1847,24 @@ static int node_order[MAX_NUMNODES];

static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
{
- enum zone_type i;
int pos, j, node;
int zone_type; /* needs to be signed */
struct zone *z;
struct zonelist *zonelist;

- for (i = 0; i < MAX_NR_ZONES; i++) {
- zonelist = pgdat->node_zonelists + i;
- pos = 0;
- for (zone_type = i; zone_type >= 0; zone_type--) {
- for (j = 0; j < nr_nodes; j++) {
- node = node_order[j];
- z = &NODE_DATA(node)->node_zones[zone_type];
- if (populated_zone(z)) {
- zonelist->zones[pos++] = z;
- check_highest_zone(zone_type);
- }
+ zonelist = &pgdat->node_zonelist;
+ pos = 0;
+ for (zone_type = MAX_NR_ZONES-1; zone_type >= 0; zone_type--) {
+ for (j = 0; j < nr_nodes; j++) {
+ node = node_order[j];
+ z = &NODE_DATA(node)->node_zones[zone_type];
+ if (populated_zone(z)) {
+ zonelist->zones[pos++] = z;
+ check_highest_zone(zone_type);
}
}
- zonelist->zones[pos] = NULL;
}
+ zonelist->zones[pos] = NULL;
}

static int default_zonelist_order(void)
@@ -1933,17 +1931,14 @@ static void set_zonelist_order(void)
static void build_zonelists(pg_data_t *pgdat)
{
int j, node, load;
- enum zone_type i;
nodemask_t used_mask;
int local_node, prev_node;
struct zonelist *zonelist;
int order = current_zonelist_order;

- /* initialize zonelists */
- for (i = 0; i < MAX_NR_ZONES; i++) {
- zonelist = pgdat->node_zonelists + i;
- zonelist->zones[0] = NULL;
- }
+ /* initialize zonelist */
+ zonelist = &pgdat->node_zonelist;
+ zonelist->zones[0] = NULL;

/* NUMA-aware ordering of nodes */
local_node = pgdat->node_id;
@@ -1997,7 +1992,7 @@ static void build_zonelist_cache(pg_data_t *pgdat)
struct zonelist_cache *zlc;
struct zone **z;

- zonelist = pgdat->node_zonelists + i;
+ zonelist = &pgdat->node_zonelist;
zonelist->zlcache_ptr = zlc = &zonelist->zlcache;
bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
for (z = zonelist->zones; *z; z++)
@@ -2016,36 +2011,36 @@ static void set_zonelist_order(void)
static void build_zonelists(pg_data_t *pgdat)
{
int node, local_node;
- enum zone_type i,j;
+ enum zone_type j;
+ struct zonelist *zonelist;

local_node = pgdat->node_id;
- for (i = 0; i < MAX_NR_ZONES; i++) {
- struct zonelist *zonelist;

- zonelist = pgdat->node_zonelists + i;
-
- j = build_zonelists_node(pgdat, zonelist, 0, i);
- /*
- * Now we build the zonelist so that it contains the zones
- * of all the other nodes.
- * We don't want to pressure a particular node, so when
- * building the zones for node N, we make sure that the
- * zones coming right after the local ones are those from
- * node N+1 (modulo N)
- */
- for (node = local_node + 1; node < MAX_NUMNODES; node++) {
- if (!node_online(node))
- continue;
- j = build_zonelists_node(NODE_DATA(node), zonelist, j, i);
- }
- for (node = 0; node < local_node; node++) {
- if (!node_online(node))
- continue;
- j = build_zonelists_node(NODE_DATA(node), zonelist, j, i);
- }
+ zonelist = &pgdat->node_zonelist;
+ j = build_zonelists_node(pgdat, zonelist, 0, MAX_NR_ZONES-1);

- zonelist->zones[j] = NULL;
+ /*
+ * Now we build the zonelist so that it contains the zones
+ * of all the other nodes.
+ * We don't want to pressure a particular node, so when
+ * building the zones for node N, we make sure that the
+ * zones coming right after the local ones are those from
+ * node N+1 (modulo N)
+ */
+ for (node = local_node + 1; node < MAX_NUMNODES; node++) {
+ if (!node_online(node))
+ continue;
+ j = build_zonelists_node(NODE_DATA(node), zonelist, j,
+ MAX_NR_ZONES-1);
}
+ for (node = 0; node < local_node; node++) {
+ if (!node_online(node))
+ continue;
+ j = build_zonelists_node(NODE_DATA(node), zonelist, j,
+ MAX_NR_ZONES-1);
+ }
+
+ zonelist->zones[j] = NULL;
}

/* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
@@ -2054,7 +2049,7 @@ static void build_zonelist_cache(pg_data_t *pgdat)
int i;

for (i = 0; i < MAX_NR_ZONES; i++)
- pgdat->node_zonelists[i].zlcache_ptr = NULL;
+ pgdat->node_zonelist.zlcache_ptr = NULL;
}

#endif /* CONFIG_NUMA */
@@ -2940,6 +2935,7 @@ static void __meminit free_area_init_core(struct pglist_data *pgdat,
nr_kernel_pages += realsize;
nr_all_pages += realsize;

+ zone->zone_idx = j;
zone->spanned_pages = size;
zone->present_pages = realsize;
#ifdef CONFIG_NUMA
diff --git a/mm/slab.c b/mm/slab.c
index a684778..558cf96 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3216,12 +3216,12 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
struct zone **z;
void *obj = NULL;
int nid;
+ enum zone_type highest_zoneidx = gfp_zone(flags);

if (flags & __GFP_THISNODE)
return NULL;

- zonelist = &NODE_DATA(slab_node(current->mempolicy))
- ->node_zonelists[gfp_zone(flags)];
+ zonelist = &NODE_DATA(slab_node(current->mempolicy))->node_zonelist;
local_flags = (flags & GFP_LEVEL_MASK);

retry:
@@ -3230,6 +3230,9 @@ retry:
* from existing per node queues.
*/
for (z = zonelist->zones; *z && !obj; z++) {
+ if (should_filter_zone(*z, highest_zoneidx))
+ continue;
+
nid = zone_to_nid(*z);

if (cpuset_zone_allowed_hardwall(*z, flags) &&
diff --git a/mm/slub.c b/mm/slub.c
index 6c6d74f..eea184b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1276,6 +1276,7 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags)
struct zonelist *zonelist;
struct zone **z;
struct page *page;
+ enum zone_type highest_zoneidx = gfp_zone(flags);

/*
* The defrag ratio allows a configuration of the tradeoffs between
@@ -1298,11 +1299,13 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags)
if (!s->defrag_ratio || get_cycles() % 1024 > s->defrag_ratio)
return NULL;

- zonelist = &NODE_DATA(slab_node(current->mempolicy))
- ->node_zonelists[gfp_zone(flags)];
+ zonelist = &NODE_DATA(slab_node(current->mempolicy))->node_zonelist;
for (z = zonelist->zones; *z; z++) {
struct kmem_cache_node *n;

+ if (should_filter_zone(*z, highest_zoneidx))
+ continue;
+
n = get_node(s, zone_to_nid(*z));

if (n && cpuset_zone_allowed_hardwall(*z, flags) &&
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d419e10..8672d61 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1124,6 +1124,7 @@ unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)
unsigned long nr_reclaimed = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
unsigned long lru_pages = 0;
+ enum zone_type highest_zoneidx;
int i;
struct scan_control sc = {
.gfp_mask = gfp_mask,
@@ -1136,9 +1137,14 @@ unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)

count_vm_event(ALLOCSTALL);

+ highest_zoneidx = gfp_zone(gfp_mask);
+
for (i = 0; zones[i] != NULL; i++) {
struct zone *zone = zones[i];

+ if (should_filter_zone(zone, highest_zoneidx))
+ continue;
+
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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