Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757752Ab0D3QvN (ORCPT ); Fri, 30 Apr 2010 12:51:13 -0400 Received: from relay1.sgi.com ([192.48.179.29]:38854 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757637Ab0D3QvC (ORCPT ); Fri, 30 Apr 2010 12:51:02 -0400 Date: Thu, 29 Apr 2010 15:09:51 -0500 From: Jack Steiner To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] - Randomize node rotor used in cpuset_mem_spread_node() Message-ID: <20100429200950.GB8929@sgi.com> References: <20100428131158.GA2648@sgi.com> <20100428150432.GA3137@sgi.com> <20100428154034.fb823484.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100428154034.fb823484.akpm@linux-foundation.org> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4782 Lines: 133 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 --- 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 #include #include +#include #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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/