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. arch/x86/mm/numa.c | 17 +++++++++++++++++ include/linux/bitmap.h | 1 + include/linux/nodemask.h | 5 +++++ kernel/fork.c | 4 ++++ lib/bitmap.c | 19 +++++++++++++++++++ 5 files changed, 46 insertions(+) Index: linux/arch/x86/mm/numa.c =================================================================== --- linux.orig/arch/x86/mm/numa.c 2010-04-28 09:44:52.422898844 -0500 +++ linux/arch/x86/mm/numa.c 2010-04-28 09:49:39.282899779 -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_find_nth_bit(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 09:44:52.494903609 -0500 +++ linux/include/linux/bitmap.h 2010-04-28 09:45:24.952154639 -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_find_nth_bit(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 09:44:52.494903609 -0500 +++ linux/include/linux/nodemask.h 2010-04-28 09:45:24.984152911 -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 09:44:52.494903609 -0500 +++ linux/kernel/fork.c 2010-04-28 09:49:39.282899779 -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 09:44:52.494903609 -0500 +++ linux/lib/bitmap.c 2010-04-28 09:49:39.282899779 -0500 @@ -1098,3 +1098,22 @@ void bitmap_copy_le(void *dst, const uns } } EXPORT_SYMBOL(bitmap_copy_le); + +/** + * bitmap_find_nth_bit(buf, ord, bits) + * @buf: pointer to bitmap + * @n: ordinal bit position (n-th set bit, n >= 0) + * @nbits: number of bits in the bitmap + * + * find the Nth bit that is set in the bitmap + * Value of @n should be in range 0 <= @n < weight(buf), else + * results are undefined. + * + * The bit positions 0 through @bits are valid positions in @buf. + */ +int bitmap_find_nth_bit(const unsigned long *bitmap, int n, int bits) +{ + return bitmap_ord_to_pos(bitmap, n, bits); +} +EXPORT_SYMBOL(bitmap_find_nth_bit); + -- 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>