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Commit 0ac0c0d0 authored by Jack Steiner's avatar Jack Steiner Committed by Linus Torvalds
Browse files

cpusets: randomize node rotor used in cpuset_mem_spread_node() 



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]
Signed-off-by: default avatarJack Steiner <steiner@sgi.com>
Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.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>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6adef3eb

arch/x86/mm/numa.c

+17 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/topology.h>

#include <linux/module.h>

#include <linux/bootmem.h>

#include <linux/random.h>



#ifdef CONFIG_DEBUG_PER_CPU_MAPS

# define DBG(x...) printk(KERN_DEBUG x)
@@ -65,3 +66,19 @@ const struct cpumask *cpumask_of_node(int node) 
}

EXPORT_SYMBOL(cpumask_of_node);

#endif



/*

 * Return the bit number of a random bit set in the nodemask.

 *   (returns -1 if nodemask is empty)

 */

int __node_random(const nodemask_t *maskp)

{

	int w, bit = -1;



	w = nodes_weight(*maskp);

	if (w)

		bit = bitmap_ord_to_pos(maskp->bits,

			get_random_int() % w, MAX_NUMNODES);

	return bit;

}

EXPORT_SYMBOL(__node_random);

include/linux/bitmap.h

+1 −0
Original line number Diff line number Diff line
@@ -141,6 +141,7 @@ 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

+8 −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 +432,10 @@ static inline void node_set_offline(int nid) 
	node_clear_state(nid, N_ONLINE);

	nr_online_nodes = num_node_state(N_ONLINE);

}



#define node_random(mask) __node_random(&(mask))

extern int __node_random(const nodemask_t *maskp);



#else



static inline int node_state(int node, enum node_states state)
@@ -460,6 +466,8 @@ 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)



static inline int node_random(const nodemask_t mask) { return 0; }

#endif



#define node_online_map 	node_states[N_ONLINE]

kernel/fork.c

+4 −0
Original line number Diff line number Diff line
@@ -1079,6 +1079,10 @@ 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 = node_random(p->mems_allowed);

	p->cpuset_slab_spread_rotor = node_random(p->mems_allowed);

#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
@@ -672,7 +672,7 @@ 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;