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    Contents of /trunk/kernel26-magellan/patches-2.6.21-r12/0012-2.6.21-mm-convert_swappiness_to_mapped.patch

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    Revision 319 - (show annotations) (download)
    Sun Aug 19 18:14:21 2007 UTC (16 years, 8 months ago) by niro
    File size: 7538 byte(s) 
    -2.6.21-magellan-r13
    1 Turn the "swappiness" knob into one with well defined semantics. Rename it
    2 "mapped" to correspond directly with the percentage of mapped ram or
    3 "applications" as users think of it. Currently the swappiness algorithm can
    4 easily lead to swapping situations on simple file copies due to the distress
    5 algorithm which too easily overrides the swappiness value. Add a
    6 "hardmaplimit" tunable, on by default, which only allows the vm to override
    7 the "mapped" tunable when distress is at its greatest to prevent false
    8 out-of-memory situations.
    9
    10 Signed-off-by: Con Kolivas <kernel@kolivas.org>
    11
    12 Documentation/sysctl/vm.txt | 23 +++++++++++++++++++++++
    13 include/linux/swap.h | 3 ++-
    14 include/linux/sysctl.h | 2 +-
    15 kernel/sysctl.c | 16 ++++++++++++----
    16 mm/vmscan.c | 27 ++++++++++++++++-----------
    17 5 files changed, 54 insertions(+), 17 deletions(-)
    18
    19 Index: linux-2.6.21-ck2/include/linux/swap.h
    20 ===================================================================
    21 --- linux-2.6.21-ck2.orig/include/linux/swap.h 2007-05-14 19:49:55.000000000 +1000
    22 +++ linux-2.6.21-ck2/include/linux/swap.h 2007-05-14 19:49:55.000000000 +1000
    23 @@ -191,7 +191,8 @@ extern void swap_setup(void);
    24 /* linux/mm/vmscan.c */
    25 extern unsigned long try_to_free_pages(struct zone **, gfp_t);
    26 extern unsigned long shrink_all_memory(unsigned long nr_pages);
    27 -extern int vm_swappiness;
    28 +extern int vm_mapped;
    29 +extern int vm_hardmaplimit;
    30 extern int remove_mapping(struct address_space *mapping, struct page *page);
    31 extern long vm_total_pages;
    32
    33 Index: linux-2.6.21-ck2/include/linux/sysctl.h
    34 ===================================================================
    35 --- linux-2.6.21-ck2.orig/include/linux/sysctl.h 2007-05-14 19:49:19.000000000 +1000
    36 +++ linux-2.6.21-ck2/include/linux/sysctl.h 2007-05-14 19:49:55.000000000 +1000
    37 @@ -190,7 +190,7 @@ enum
    38 VM_OVERCOMMIT_RATIO=16, /* percent of RAM to allow overcommit in */
    39 VM_PAGEBUF=17, /* struct: Control pagebuf parameters */
    40 VM_HUGETLB_PAGES=18, /* int: Number of available Huge Pages */
    41 - VM_SWAPPINESS=19, /* Tendency to steal mapped memory */
    42 + VM_MAPPED=19, /* percent mapped min while evicting cache */
    43 VM_LOWMEM_RESERVE_RATIO=20,/* reservation ratio for lower memory zones */
    44 VM_MIN_FREE_KBYTES=21, /* Minimum free kilobytes to maintain */
    45 VM_MAX_MAP_COUNT=22, /* int: Maximum number of mmaps/address-space */
    46 Index: linux-2.6.21-ck2/kernel/sysctl.c
    47 ===================================================================
    48 --- linux-2.6.21-ck2.orig/kernel/sysctl.c 2007-05-14 19:49:55.000000000 +1000
    49 +++ linux-2.6.21-ck2/kernel/sysctl.c 2007-05-14 19:49:55.000000000 +1000
    50 @@ -741,16 +741,24 @@ static ctl_table vm_table[] = {
    51 .proc_handler = &proc_dointvec,
    52 },
    53 {
    54 - .ctl_name = VM_SWAPPINESS,
    55 - .procname = "swappiness",
    56 - .data = &vm_swappiness,
    57 - .maxlen = sizeof(vm_swappiness),
    58 + .ctl_name = CTL_UNNUMBERED,
    59 + .procname = "mapped",
    60 + .data = &vm_mapped,
    61 + .maxlen = sizeof(vm_mapped),
    62 .mode = 0644,
    63 .proc_handler = &proc_dointvec_minmax,
    64 .strategy = &sysctl_intvec,
    65 .extra1 = &zero,
    66 .extra2 = &one_hundred,
    67 },
    68 + {
    69 + .ctl_name = CTL_UNNUMBERED,
    70 + .procname = "hardmaplimit",
    71 + .data = &vm_hardmaplimit,
    72 + .maxlen = sizeof(int),
    73 + .mode = 0644,
    74 + .proc_handler = &proc_dointvec,
    75 + },
    76 #ifdef CONFIG_HUGETLB_PAGE
    77 {
    78 .ctl_name = VM_HUGETLB_PAGES,
    79 Index: linux-2.6.21-ck2/mm/vmscan.c
    80 ===================================================================
    81 --- linux-2.6.21-ck2.orig/mm/vmscan.c 2007-05-14 19:49:55.000000000 +1000
    82 +++ linux-2.6.21-ck2/mm/vmscan.c 2007-05-14 19:49:55.000000000 +1000
    83 @@ -64,7 +64,7 @@ struct scan_control {
    84 * whole list at once. */
    85 int swap_cluster_max;
    86
    87 - int swappiness;
    88 + int mapped;
    89
    90 int all_unreclaimable;
    91 };
    92 @@ -111,9 +111,10 @@ struct shrinker {
    93 #endif
    94
    95 /*
    96 - * From 0 .. 100. Higher means more swappy.
    97 + * From 0 .. 100. Lower means more swappy.
    98 */
    99 -int vm_swappiness = 60;
    100 +int vm_mapped __read_mostly = 66;
    101 +int vm_hardmaplimit __read_mostly = 1;
    102 long vm_total_pages; /* The total number of pages which the VM controls */
    103
    104 static LIST_HEAD(shrinker_list);
    105 @@ -809,10 +810,14 @@ static void shrink_active_list(unsigned
    106 * The distress ratio is important - we don't want to start
    107 * going oom.
    108 *
    109 - * A 100% value of vm_swappiness overrides this algorithm
    110 - * altogether.
    111 + * This distress value is ignored if we apply a hardmaplimit except
    112 + * in extreme distress.
    113 + *
    114 + * A 0% value of vm_mapped overrides this algorithm altogether.
    115 */
    116 - swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
    117 + swap_tendency = mapped_ratio * 100 / (sc->mapped + 1);
    118 + if (!vm_hardmaplimit || distress == 100)
    119 + swap_tendency += distress;
    120
    121 /*
    122 * Now use this metric to decide whether to start moving mapped
    123 @@ -1031,7 +1036,7 @@ unsigned long try_to_free_pages(struct z
    124 .may_writepage = !laptop_mode,
    125 .swap_cluster_max = SWAP_CLUSTER_MAX,
    126 .may_swap = 1,
    127 - .swappiness = vm_swappiness,
    128 + .mapped = vm_mapped,
    129 };
    130
    131 delay_swap_prefetch();
    132 @@ -1138,7 +1143,7 @@ static unsigned long balance_pgdat(pg_da
    133 .gfp_mask = GFP_KERNEL,
    134 .may_swap = 1,
    135 .swap_cluster_max = SWAP_CLUSTER_MAX,
    136 - .swappiness = vm_swappiness,
    137 + .mapped = vm_mapped,
    138 };
    139 /*
    140 * temp_priority is used to remember the scanning priority at which
    141 @@ -1446,7 +1451,7 @@ unsigned long shrink_all_memory(unsigned
    142 .may_swap = 0,
    143 .swap_cluster_max = nr_pages,
    144 .may_writepage = 1,
    145 - .swappiness = vm_swappiness,
    146 + .mapped = vm_mapped,
    147 };
    148
    149 current->reclaim_state = &reclaim_state;
    150 @@ -1481,7 +1486,7 @@ unsigned long shrink_all_memory(unsigned
    151 /* Force reclaiming mapped pages in the passes #3 and #4 */
    152 if (pass > 2) {
    153 sc.may_swap = 1;
    154 - sc.swappiness = 100;
    155 + sc.mapped = 0;
    156 }
    157
    158 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
    159 @@ -1629,7 +1634,7 @@ static int __zone_reclaim(struct zone *z
    160 .swap_cluster_max = max_t(unsigned long, nr_pages,
    161 SWAP_CLUSTER_MAX),
    162 .gfp_mask = gfp_mask,
    163 - .swappiness = vm_swappiness,
    164 + .mapped = vm_mapped,
    165 };
    166 unsigned long slab_reclaimable;
    167
    168 Index: linux-2.6.21-ck2/Documentation/sysctl/vm.txt
    169 ===================================================================
    170 --- linux-2.6.21-ck2.orig/Documentation/sysctl/vm.txt 2007-05-14 19:49:55.000000000 +1000
    171 +++ linux-2.6.21-ck2/Documentation/sysctl/vm.txt 2007-05-14 19:49:55.000000000 +1000
    172 @@ -22,6 +22,8 @@ Currently, these files are in /proc/sys/
    173 - dirty_background_ratio
    174 - dirty_expire_centisecs
    175 - dirty_writeback_centisecs
    176 +- hardmaplimit
    177 +- mapped
    178 - max_map_count
    179 - min_free_kbytes
    180 - laptop_mode
    181 @@ -87,6 +89,27 @@ for swap because we only cluster swap da
    182
    183 ==============================================================
    184
    185 +hardmaplimit:
    186 +
    187 +This flag makes the vm adhere to the mapped value as closely as possible
    188 +except in the most extreme vm stress where doing so would provoke an out
    189 +of memory condition (see mapped below).
    190 +
    191 +Enabled by default.
    192 +
    193 +==============================================================
    194 +
    195 +mapped:
    196 +
    197 +This is the percentage ram that is filled with mapped pages (applications)
    198 +before the vm will start reclaiming mapped pages by moving them to swap.
    199 +It is altered by the relative stress of the vm at the time so is not
    200 +strictly adhered to to prevent provoking out of memory kills.
    201 +
    202 +Set to 66 by default.
    203 +
    204 +==============================================================
    205 +
    206 max_map_count:
    207
    208 This file contains the maximum number of memory map areas a process