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Commit 778d3b0f authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
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cpusets: randomize node rotor used in cpuset_mem_spread_node() 



[ This patch has already been accepted as commit 0ac0c0d0 but later
  reverted (commit 35926ff5) because it itroduced arch specific
  __node_random which was defined only for x86 code so it broke other
  archs.  This is a followup without any arch specific code.  Other than
  that there are no functional changes.]

Some workloads that create a large number of small files tend to assign
too many pages to node 0 (multi-node systems).  Part of the reason is
that the rotor (in cpuset_mem_spread_node()) used to assign nodes starts
at node 0 for newly created tasks.

This patch changes the rotor to be initialized to a random node number
of the cpuset.

[akpm@linux-foundation.org: fix layout]
[Lee.Schermerhorn@hp.com: Define stub numa_random() for !NUMA configuration]
[mhocko@suse.cz: Make it arch independent]
[akpm@linux-foundation.org: fix CONFIG_NUMA=y, MAX_NUMNODES>1 build]
Signed-off-by: default avatarJack Steiner <steiner@sgi.com>
Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Paul Menage <menage@google.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Robin Holt <holt@sgi.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Paul Menage <menage@google.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8521fc50

include/linux/bitmap.h

+1 −0
Original line number Diff line number Diff line
@@ -144,6 +144,7 @@ extern int bitmap_find_free_region(unsigned long *bitmap, int bits, int order); 
extern void bitmap_release_region(unsigned long *bitmap, int pos, int order);

extern int bitmap_allocate_region(unsigned long *bitmap, int pos, int order);

extern void bitmap_copy_le(void *dst, const unsigned long *src, int nbits);

extern int bitmap_ord_to_pos(const unsigned long *bitmap, int n, int bits);



#define BITMAP_LAST_WORD_MASK(nbits)					\

(									\

include/linux/nodemask.h

+13 −0
Original line number Diff line number Diff line
@@ -66,6 +66,8 @@ 
 * int num_online_nodes()		Number of online Nodes

 * int num_possible_nodes()		Number of all possible Nodes

 *

 * int node_random(mask)		Random node with set bit in mask

 *

 * int node_online(node)		Is some node online?

 * int node_possible(node)		Is some node possible?

 *
@@ -430,6 +432,7 @@ static inline void node_set_offline(int nid) 
	node_clear_state(nid, N_ONLINE);

	nr_online_nodes = num_node_state(N_ONLINE);

}



#else



static inline int node_state(int node, enum node_states state)
@@ -460,6 +463,16 @@ static inline int num_node_state(enum node_states state) 


#define node_set_online(node)	   node_set_state((node), N_ONLINE)

#define node_set_offline(node)	   node_clear_state((node), N_ONLINE)



#endif



#if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)

extern int node_random(const nodemask_t *maskp);

#else

static inline int node_random(const nodemask_t *mask)

{

	return 0;

}

#endif



#define node_online_map 	node_states[N_ONLINE]

kernel/cpuset.c

+8 −0
Original line number Diff line number Diff line
@@ -2460,11 +2460,19 @@ static int cpuset_spread_node(int *rotor) 


int cpuset_mem_spread_node(void)

{

	if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)

		current->cpuset_mem_spread_rotor =

			node_random(&current->mems_allowed);



	return cpuset_spread_node(&current->cpuset_mem_spread_rotor);

}



int cpuset_slab_spread_node(void)

{

	if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)

		current->cpuset_slab_spread_rotor =

			node_random(&current->mems_allowed);



	return cpuset_spread_node(&current->cpuset_slab_spread_rotor);

}

kernel/fork.c

+4 −0
Original line number Diff line number Diff line
@@ -1173,6 +1173,10 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
 	}

	mpol_fix_fork_child_flag(p);

#endif

#ifdef CONFIG_CPUSETS

	p->cpuset_mem_spread_rotor = NUMA_NO_NODE;

	p->cpuset_slab_spread_rotor = NUMA_NO_NODE;

#endif

#ifdef CONFIG_TRACE_IRQFLAGS

	p->irq_events = 0;

#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW

lib/bitmap.c

+1 −1
Original line number Diff line number Diff line
@@ -756,7 +756,7 @@ static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits) 
 *

 * The bit positions 0 through @bits are valid positions in @buf.

 */

static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)

int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)

{

	int pos = 0;