5 files changed, 81 insertions, 0 deletions

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 89ba1a42a17d..6910c0136f8d 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -103,3 +103,20 @@ This is used to force the Linux VM to keep a minimum number
 of kilobytes free.  The VM uses this number to compute a pages_min
 value for each lowmem zone in the system.  Each lowmem zone gets 
 a number of reserved free pages based proportionally on its size.
+
+==============================================================
+
+percpu_pagelist_fraction
+
+This is the fraction of pages at most (high mark pcp->high) in each zone that
+are allocated for each per cpu page list.  The min value for this is 8.  It
+means that we don't allow more than 1/8th of pages in each zone to be
+allocated in any single per_cpu_pagelist.  This entry only changes the value
+of hot per cpu pagelists.  User can specify a number like 100 to allocate
+1/100th of each zone to each per cpu page list.
+
+The batch value of each per cpu pagelist is also updated as a result.  It is
+set to pcp->high/4.  The upper limit of batch is (PAGE_SHIFT * 8)
+
+The initial value is zero.  Kernel does not use this value at boot time to set
+the high water marks for each per cpu page list.
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index c34f4a2c62f8..2a89c132ba9c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -437,6 +437,8 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *, int, struct file *,
 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, struct file *,
                                         void __user *, size_t *, loff_t *);
+int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int, struct file *,
+                                        void __user *, size_t *, loff_t *);
 
 #include <linux/topology.h>
 /* Returns the number of the current Node. */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 4cd267fe87ec..7f472127b7b5 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -181,6 +181,7 @@ enum
         VM_LEGACY_VA_LAYOUT=27, /* legacy/compatibility virtual address space layout */
         VM_SWAP_TOKEN_TIMEOUT=28, /* default time for token time out */
         VM_DROP_PAGECACHE=29,   /* int: nuke lots of pagecache */
+        VM_PERCPU_PAGELIST_FRACTION=30,/* int: fraction of pages in each percpu_pagelist */
 };
 
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8dcf6fd5b0f9..03b0598f2369 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -69,6 +69,7 @@ extern int printk_ratelimit_jiffies;
 extern int printk_ratelimit_burst;
 extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
+extern int percpu_pagelist_fraction;
 
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 int unknown_nmi_panic;
@@ -79,6 +80,7 @@ extern int proc_unknown_nmi_panic(ctl_table *, int, struct file *,
 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
 static int maxolduid = 65535;
 static int minolduid;
+static int min_percpu_pagelist_fract = 8;
 
 static int ngroups_max = NGROUPS_MAX;
 
@@ -794,6 +796,16 @@ static ctl_table vm_table[] = {
                 .strategy       = &sysctl_intvec,
                 .extra1         = &zero,
         },
+        {
+                .ctl_name       = VM_PERCPU_PAGELIST_FRACTION,
+                .procname       = "percpu_pagelist_fraction",
+                .data           = &percpu_pagelist_fraction,
+                .maxlen         = sizeof(percpu_pagelist_fraction),
+                .mode           = 0644,
+                .proc_handler   = &percpu_pagelist_fraction_sysctl_handler,
+                .strategy       = &sysctl_intvec,
+                .extra1         = &min_percpu_pagelist_fract,
+        },
 #ifdef CONFIG_MMU
         {
                 .ctl_name       = VM_MAX_MAP_COUNT,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5eeeadd9f66a..2c46f697e8ff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -53,6 +53,7 @@ struct pglist_data *pgdat_list __read_mostly;
 unsigned long totalram_pages __read_mostly;
 unsigned long totalhigh_pages __read_mostly;
 long nr_swap_pages;
+int percpu_pagelist_fraction;
 
 static void fastcall free_hot_cold_page(struct page *page, int cold);
 
@@ -1831,6 +1832,24 @@ inline void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
         INIT_LIST_HEAD(&pcp->list);
 }
 
+/*
+ * setup_pagelist_highmark() sets the high water mark for hot per_cpu_pagelist
+ * to the value high for the pageset p.
+ */
+
+static void setup_pagelist_highmark(struct per_cpu_pageset *p,
+                                unsigned long high)
+{
+        struct per_cpu_pages *pcp;
+
+        pcp = &p->pcp[0]; /* hot list */
+        pcp->high = high;
+        pcp->batch = max(1UL, high/4);
+        if ((high/4) > (PAGE_SHIFT * 8))
+                pcp->batch = PAGE_SHIFT * 8;
+}
+
+
 #ifdef CONFIG_NUMA
 /*
  * Boot pageset table. One per cpu which is going to be used for all
@@ -1868,6 +1887,10 @@ static int __devinit process_zones(int cpu)
                         goto bad;
 
                 setup_pageset(zone->pageset[cpu], zone_batchsize(zone));
+
+                if (percpu_pagelist_fraction)
+                        setup_pagelist_highmark(zone_pcp(zone, cpu),
+                                (zone->present_pages / percpu_pagelist_fraction));
         }
 
         return 0;
@@ -2567,6 +2590,32 @@ int lowmem_reserve_ratio_sysctl_handler(ctl_table *table, int write,
         return 0;
 }
 
+/*
+ * percpu_pagelist_fraction - changes the pcp->high for each zone on each
+ * cpu.  It is the fraction of total pages in each zone that a hot per cpu pagelist
+ * can have before it gets flushed back to buddy allocator.
+ */
+
+int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
+        struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
+{
+        struct zone *zone;
+        unsigned int cpu;
+        int ret;
+
+        ret = proc_dointvec_minmax(table, write, file, buffer, length, ppos);
+        if (!write || (ret == -EINVAL))
+                return ret;
+        for_each_zone(zone) {
+                for_each_online_cpu(cpu) {
+                        unsigned long  high;
+                        high = zone->present_pages / percpu_pagelist_fraction;
+                        setup_pagelist_highmark(zone_pcp(zone, cpu), high);
+                }
+        }
+        return 0;
+}
+
 __initdata int hashdist = HASHDIST_DEFAULT;
 
 #ifdef CONFIG_NUMA