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![Feng Tang](/assets/img/avatar_default.png)
When checking a performance change for will-it-scale scalability mmap test [1], we found very high lock contention for spinlock of percpu counter 'vm_committed_as': 94.14% 0.35% [kernel.kallsyms] [k] _raw_spin_lock_irqsave 48.21% _raw_spin_lock_irqsave;percpu_counter_add_batch;__vm_enough_memory;mmap_region;do_mmap; 45.91% _raw_spin_lock_irqsave;percpu_counter_add_batch;__do_munmap; Actually this heavy lock contention is not always necessary. The 'vm_committed_as' needs to be very precise when the strict OVERCOMMIT_NEVER policy is set, which requires a rather small batch number for the percpu counter. So keep 'batch' number unchanged for strict OVERCOMMIT_NEVER policy, and lift it to 64X for OVERCOMMIT_ALWAYS and OVERCOMMIT_GUESS policies. Also add a sysctl handler to adjust it when the policy is reconfigured. Benchmark with the same testcase in [1] shows 53% improvement on a 8C/16T desktop, and 2097%(20X) on a 4S/72C/144T server. We tested with test platforms in 0day (server, desktop and laptop), and 80%+ platforms shows improvements with that test. And whether it shows improvements depends on if the test mmap size is bigger than the batch number computed. And if the lift is 16X, 1/3 of the platforms will show improvements, though it should help the mmap/unmap usage generally, as Michal Hocko mentioned: : I believe that there are non-synthetic worklaods which would benefit from : a larger batch. E.g. large in memory databases which do large mmaps : during startups from multiple threads. [1] https://lore.kernel.org/lkml/20200305062138.GI5972@shao2-debian/ Signed-off-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Qian Cai <cai@lca.pw> Cc: Kees Cook <keescook@chromium.org> Cc: Andi Kleen <andi.kleen@intel.com> Cc: Tim Chen <tim.c.chen@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: Christoph Lameter <cl@linux.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: kernel test robot <rong.a.chen@intel.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/1589611660-89854-4-git-send-email-feng.tang@intel.com Link: http://lkml.kernel.org/r/1592725000-73486-4-git-send-email-feng.tang@intel.com Link: http://lkml.kernel.org/r/1594389708-60781-5-git-send-email-feng.tang@intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
207 lines
5.3 KiB
C
207 lines
5.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* mm_init.c - Memory initialisation verification and debugging
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*
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* Copyright 2008 IBM Corporation, 2008
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* Author Mel Gorman <mel@csn.ul.ie>
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*
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/kobject.h>
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#include <linux/export.h>
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#include <linux/memory.h>
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#include <linux/notifier.h>
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#include <linux/sched.h>
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#include <linux/mman.h>
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#include "internal.h"
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#ifdef CONFIG_DEBUG_MEMORY_INIT
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int __meminitdata mminit_loglevel;
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#ifndef SECTIONS_SHIFT
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#define SECTIONS_SHIFT 0
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#endif
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/* The zonelists are simply reported, validation is manual. */
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void __init mminit_verify_zonelist(void)
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{
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int nid;
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if (mminit_loglevel < MMINIT_VERIFY)
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return;
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for_each_online_node(nid) {
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pg_data_t *pgdat = NODE_DATA(nid);
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struct zone *zone;
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struct zoneref *z;
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struct zonelist *zonelist;
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int i, listid, zoneid;
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BUILD_BUG_ON(MAX_ZONELISTS > 2);
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for (i = 0; i < MAX_ZONELISTS * MAX_NR_ZONES; i++) {
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/* Identify the zone and nodelist */
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zoneid = i % MAX_NR_ZONES;
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listid = i / MAX_NR_ZONES;
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zonelist = &pgdat->node_zonelists[listid];
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zone = &pgdat->node_zones[zoneid];
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if (!populated_zone(zone))
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continue;
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/* Print information about the zonelist */
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printk(KERN_DEBUG "mminit::zonelist %s %d:%s = ",
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listid > 0 ? "thisnode" : "general", nid,
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zone->name);
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/* Iterate the zonelist */
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for_each_zone_zonelist(zone, z, zonelist, zoneid)
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pr_cont("%d:%s ", zone_to_nid(zone), zone->name);
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pr_cont("\n");
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}
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}
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}
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void __init mminit_verify_pageflags_layout(void)
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{
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int shift, width;
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unsigned long or_mask, add_mask;
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shift = 8 * sizeof(unsigned long);
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width = shift - SECTIONS_WIDTH - NODES_WIDTH - ZONES_WIDTH
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- LAST_CPUPID_SHIFT - KASAN_TAG_WIDTH;
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_widths",
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"Section %d Node %d Zone %d Lastcpupid %d Kasantag %d Flags %d\n",
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SECTIONS_WIDTH,
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NODES_WIDTH,
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ZONES_WIDTH,
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LAST_CPUPID_WIDTH,
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KASAN_TAG_WIDTH,
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NR_PAGEFLAGS);
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_shifts",
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"Section %d Node %d Zone %d Lastcpupid %d Kasantag %d\n",
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SECTIONS_SHIFT,
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NODES_SHIFT,
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ZONES_SHIFT,
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LAST_CPUPID_SHIFT,
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KASAN_TAG_WIDTH);
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_pgshifts",
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"Section %lu Node %lu Zone %lu Lastcpupid %lu Kasantag %lu\n",
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(unsigned long)SECTIONS_PGSHIFT,
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(unsigned long)NODES_PGSHIFT,
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(unsigned long)ZONES_PGSHIFT,
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(unsigned long)LAST_CPUPID_PGSHIFT,
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(unsigned long)KASAN_TAG_PGSHIFT);
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_nodezoneid",
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"Node/Zone ID: %lu -> %lu\n",
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(unsigned long)(ZONEID_PGOFF + ZONEID_SHIFT),
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(unsigned long)ZONEID_PGOFF);
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_usage",
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"location: %d -> %d layout %d -> %d unused %d -> %d page-flags\n",
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shift, width, width, NR_PAGEFLAGS, NR_PAGEFLAGS, 0);
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#ifdef NODE_NOT_IN_PAGE_FLAGS
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_nodeflags",
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"Node not in page flags");
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#endif
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#ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
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mminit_dprintk(MMINIT_TRACE, "pageflags_layout_nodeflags",
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"Last cpupid not in page flags");
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#endif
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if (SECTIONS_WIDTH) {
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shift -= SECTIONS_WIDTH;
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BUG_ON(shift != SECTIONS_PGSHIFT);
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}
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if (NODES_WIDTH) {
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shift -= NODES_WIDTH;
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BUG_ON(shift != NODES_PGSHIFT);
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}
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if (ZONES_WIDTH) {
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shift -= ZONES_WIDTH;
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BUG_ON(shift != ZONES_PGSHIFT);
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}
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/* Check for bitmask overlaps */
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or_mask = (ZONES_MASK << ZONES_PGSHIFT) |
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(NODES_MASK << NODES_PGSHIFT) |
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(SECTIONS_MASK << SECTIONS_PGSHIFT);
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add_mask = (ZONES_MASK << ZONES_PGSHIFT) +
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(NODES_MASK << NODES_PGSHIFT) +
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(SECTIONS_MASK << SECTIONS_PGSHIFT);
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BUG_ON(or_mask != add_mask);
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}
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static __init int set_mminit_loglevel(char *str)
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{
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get_option(&str, &mminit_loglevel);
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return 0;
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}
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early_param("mminit_loglevel", set_mminit_loglevel);
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#endif /* CONFIG_DEBUG_MEMORY_INIT */
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struct kobject *mm_kobj;
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EXPORT_SYMBOL_GPL(mm_kobj);
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#ifdef CONFIG_SMP
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s32 vm_committed_as_batch = 32;
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void mm_compute_batch(int overcommit_policy)
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{
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u64 memsized_batch;
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s32 nr = num_present_cpus();
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s32 batch = max_t(s32, nr*2, 32);
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unsigned long ram_pages = totalram_pages();
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/*
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* For policy OVERCOMMIT_NEVER, set batch size to 0.4% of
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* (total memory/#cpus), and lift it to 25% for other policies
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* to easy the possible lock contention for percpu_counter
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* vm_committed_as, while the max limit is INT_MAX
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*/
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if (overcommit_policy == OVERCOMMIT_NEVER)
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memsized_batch = min_t(u64, ram_pages/nr/256, INT_MAX);
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else
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memsized_batch = min_t(u64, ram_pages/nr/4, INT_MAX);
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vm_committed_as_batch = max_t(s32, memsized_batch, batch);
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}
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static int __meminit mm_compute_batch_notifier(struct notifier_block *self,
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unsigned long action, void *arg)
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{
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switch (action) {
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case MEM_ONLINE:
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case MEM_OFFLINE:
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mm_compute_batch(sysctl_overcommit_memory);
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default:
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break;
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}
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return NOTIFY_OK;
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}
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static struct notifier_block compute_batch_nb __meminitdata = {
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.notifier_call = mm_compute_batch_notifier,
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.priority = IPC_CALLBACK_PRI, /* use lowest priority */
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};
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static int __init mm_compute_batch_init(void)
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{
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mm_compute_batch(sysctl_overcommit_memory);
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register_hotmemory_notifier(&compute_batch_nb);
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return 0;
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}
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__initcall(mm_compute_batch_init);
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#endif
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static int __init mm_sysfs_init(void)
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{
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mm_kobj = kobject_create_and_add("mm", kernel_kobj);
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if (!mm_kobj)
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return -ENOMEM;
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return 0;
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}
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postcore_initcall(mm_sysfs_init);
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