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. NOTE: this patch is on TOP of the previous patch: [PATCH] - New round-robin rotor for SLAB allocations http://marc.info/?l=linux-mm&m=127231565321947&w=2 Signed-off-by: Jack Steiner <steiner@xxxxxxx> --- V2 - initial patch was generated against the wrong tree. This patch is based on linux-next. V3 - Eliminate new function bitmap_find_nth_bit(). Rename bitmap_ord_to_pos() and export it. arch/x86/mm/numa.c | 17 +++++++++++++++++ include/linux/bitmap.h | 1 + include/linux/nodemask.h | 5 +++++ kernel/fork.c | 4 ++++ lib/bitmap.c | 2 +- 5 files changed, 28 insertions(+), 1 deletion(-) Index: linux/arch/x86/mm/numa.c =================================================================== --- linux.orig/arch/x86/mm/numa.c 2010-04-28 09:59:10.158899192 -0500 +++ linux/arch/x86/mm/numa.c 2010-04-29 13:53:48.531783017 -0500 @@ -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(in } 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); Index: linux/include/linux/bitmap.h =================================================================== --- linux.orig/include/linux/bitmap.h 2010-04-28 09:59:10.158899192 -0500 +++ linux/include/linux/bitmap.h 2010-04-29 13:54:04.639408240 -0500 @@ -141,6 +141,7 @@ extern int bitmap_find_free_region(unsig 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) \ ( \ Index: linux/include/linux/nodemask.h =================================================================== --- linux.orig/include/linux/nodemask.h 2010-04-28 09:59:10.158899192 -0500 +++ linux/include/linux/nodemask.h 2010-04-28 10:01:42.878971800 -0500 @@ -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? * @@ -267,6 +269,9 @@ static inline int __first_unset_node(con find_first_zero_bit(maskp->bits, MAX_NUMNODES)); } +#define node_random(mask) __node_random(&(mask)) +extern int __node_random(const nodemask_t *maskp); + #define NODE_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(MAX_NUMNODES) #if MAX_NUMNODES <= BITS_PER_LONG Index: linux/kernel/fork.c =================================================================== --- linux.orig/kernel/fork.c 2010-04-28 09:59:10.158899192 -0500 +++ linux/kernel/fork.c 2010-04-28 10:03:11.580014823 -0500 @@ -1079,6 +1079,10 @@ static struct task_struct *copy_process( } 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 Index: linux/lib/bitmap.c =================================================================== --- linux.orig/lib/bitmap.c 2010-04-28 09:59:10.158899192 -0500 +++ linux/lib/bitmap.c 2010-04-29 13:53:28.270906295 -0500 @@ -672,7 +672,7 @@ static int bitmap_pos_to_ord(const unsig * * 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; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>