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    Contents of /trunk/kernel26-alx/patches-2.6.20-r6/0016-2.6.20-mm-convert_swappiness_to_mapped.patch

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    Revision 1175 - (show annotations) (download)
    Thu Oct 14 12:15:46 2010 UTC (13 years, 6 months ago) by niro
    File size: 7785 byte(s) 
    -2.6.20-alx-r6 new magellan 0.5.2 kernel
    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 | 3 ++-
    15 kernel/sysctl.c | 16 ++++++++++++----
    16 mm/vmscan.c | 27 ++++++++++++++++-----------
    17 5 files changed, 55 insertions(+), 17 deletions(-)
    18
    19 Index: linux-2.6.20-ck1/include/linux/swap.h
    20 ===================================================================
    21 --- linux-2.6.20-ck1.orig/include/linux/swap.h 2007-02-16 19:01:33.000000000 +1100
    22 +++ linux-2.6.20-ck1/include/linux/swap.h 2007-02-16 19:01:33.000000000 +1100
    23 @@ -189,7 +189,8 @@ 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-2.6.20-ck1/include/linux/sysctl.h
    34 ===================================================================
    35 --- linux-2.6.20-ck1.orig/include/linux/sysctl.h 2007-02-16 19:01:33.000000000 +1100
    36 +++ linux-2.6.20-ck1/include/linux/sysctl.h 2007-02-16 19:01:33.000000000 +1100
    37 @@ -185,7 +185,7 @@ 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 @@ -203,6 +203,7 @@ enum
    47 VM_VDSO_ENABLED=34, /* map VDSO into new processes? */
    48 VM_MIN_SLAB=35, /* Percent pages ignored by zone reclaim */
    49 VM_SWAP_PREFETCH=36, /* swap prefetch */
    50 + VM_HARDMAPLIMIT=37, /* Make mapped a hard limit */
    51 };
    52
    53
    54 Index: linux-2.6.20-ck1/kernel/sysctl.c
    55 ===================================================================
    56 --- linux-2.6.20-ck1.orig/kernel/sysctl.c 2007-02-16 19:01:33.000000000 +1100
    57 +++ linux-2.6.20-ck1/kernel/sysctl.c 2007-02-16 19:01:33.000000000 +1100
    58 @@ -900,16 +900,24 @@ static ctl_table vm_table[] = {
    59 .proc_handler = &proc_dointvec,
    60 },
    61 {
    62 - .ctl_name = VM_SWAPPINESS,
    63 - .procname = "swappiness",
    64 - .data = &vm_swappiness,
    65 - .maxlen = sizeof(vm_swappiness),
    66 + .ctl_name = VM_MAPPED,
    67 + .procname = "mapped",
    68 + .data = &vm_mapped,
    69 + .maxlen = sizeof(vm_mapped),
    70 .mode = 0644,
    71 .proc_handler = &proc_dointvec_minmax,
    72 .strategy = &sysctl_intvec,
    73 .extra1 = &zero,
    74 .extra2 = &one_hundred,
    75 },
    76 + {
    77 + .ctl_name = VM_HARDMAPLIMIT,
    78 + .procname = "hardmaplimit",
    79 + .data = &vm_hardmaplimit,
    80 + .maxlen = sizeof(int),
    81 + .mode = 0644,
    82 + .proc_handler = &proc_dointvec,
    83 + },
    84 #ifdef CONFIG_HUGETLB_PAGE
    85 {
    86 .ctl_name = VM_HUGETLB_PAGES,
    87 Index: linux-2.6.20-ck1/mm/vmscan.c
    88 ===================================================================
    89 --- linux-2.6.20-ck1.orig/mm/vmscan.c 2007-02-16 19:01:33.000000000 +1100
    90 +++ linux-2.6.20-ck1/mm/vmscan.c 2007-02-16 19:01:33.000000000 +1100
    91 @@ -64,7 +64,7 @@ struct scan_control {
    92 * whole list at once. */
    93 int swap_cluster_max;
    94
    95 - int swappiness;
    96 + int mapped;
    97
    98 int all_unreclaimable;
    99 };
    100 @@ -111,9 +111,10 @@ struct shrinker {
    101 #endif
    102
    103 /*
    104 - * From 0 .. 100. Higher means more swappy.
    105 + * From 0 .. 100. Lower means more swappy.
    106 */
    107 -int vm_swappiness = 60;
    108 +int vm_mapped __read_mostly = 66;
    109 +int vm_hardmaplimit __read_mostly = 1;
    110 long vm_total_pages; /* The total number of pages which the VM controls */
    111
    112 static LIST_HEAD(shrinker_list);
    113 @@ -808,10 +809,14 @@ static void shrink_active_list(unsigned
    114 * The distress ratio is important - we don't want to start
    115 * going oom.
    116 *
    117 - * A 100% value of vm_swappiness overrides this algorithm
    118 - * altogether.
    119 + * This distress value is ignored if we apply a hardmaplimit except
    120 + * in extreme distress.
    121 + *
    122 + * A 0% value of vm_mapped overrides this algorithm altogether.
    123 */
    124 - swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
    125 + swap_tendency = mapped_ratio * 100 / (sc->mapped + 1);
    126 + if (!vm_hardmaplimit || distress == 100)
    127 + swap_tendency += distress;
    128
    129 /*
    130 * Now use this metric to decide whether to start moving mapped
    131 @@ -1028,7 +1033,7 @@ unsigned long try_to_free_pages(struct z
    132 .may_writepage = !laptop_mode,
    133 .swap_cluster_max = SWAP_CLUSTER_MAX,
    134 .may_swap = 1,
    135 - .swappiness = vm_swappiness,
    136 + .mapped = vm_mapped,
    137 };
    138
    139 delay_swap_prefetch();
    140 @@ -1134,7 +1139,7 @@ static unsigned long balance_pgdat(pg_da
    141 .gfp_mask = GFP_KERNEL,
    142 .may_swap = 1,
    143 .swap_cluster_max = SWAP_CLUSTER_MAX,
    144 - .swappiness = vm_swappiness,
    145 + .mapped = vm_mapped,
    146 };
    147 /*
    148 * temp_priority is used to remember the scanning priority at which
    149 @@ -1441,7 +1446,7 @@ unsigned long shrink_all_memory(unsigned
    150 .may_swap = 0,
    151 .swap_cluster_max = nr_pages,
    152 .may_writepage = 1,
    153 - .swappiness = vm_swappiness,
    154 + .mapped = vm_mapped,
    155 };
    156
    157 current->reclaim_state = &reclaim_state;
    158 @@ -1476,7 +1481,7 @@ unsigned long shrink_all_memory(unsigned
    159 /* Force reclaiming mapped pages in the passes #3 and #4 */
    160 if (pass > 2) {
    161 sc.may_swap = 1;
    162 - sc.swappiness = 100;
    163 + sc.mapped = 0;
    164 }
    165
    166 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
    167 @@ -1624,7 +1629,7 @@ static int __zone_reclaim(struct zone *z
    168 .swap_cluster_max = max_t(unsigned long, nr_pages,
    169 SWAP_CLUSTER_MAX),
    170 .gfp_mask = gfp_mask,
    171 - .swappiness = vm_swappiness,
    172 + .mapped = vm_mapped,
    173 };
    174 unsigned long slab_reclaimable;
    175
    176 Index: linux-2.6.20-ck1/Documentation/sysctl/vm.txt
    177 ===================================================================
    178 --- linux-2.6.20-ck1.orig/Documentation/sysctl/vm.txt 2007-02-16 19:01:33.000000000 +1100
    179 +++ linux-2.6.20-ck1/Documentation/sysctl/vm.txt 2007-02-16 19:01:33.000000000 +1100
    180 @@ -22,6 +22,8 @@ Currently, these files are in /proc/sys/
    181 - dirty_background_ratio
    182 - dirty_expire_centisecs
    183 - dirty_writeback_centisecs
    184 +- hardmaplimit
    185 +- mapped
    186 - max_map_count
    187 - min_free_kbytes
    188 - laptop_mode
    189 @@ -87,6 +89,27 @@ for swap because we only cluster swap da
    190
    191 ==============================================================
    192
    193 +hardmaplimit:
    194 +
    195 +This flag makes the vm adhere to the mapped value as closely as possible
    196 +except in the most extreme vm stress where doing so would provoke an out
    197 +of memory condition (see mapped below).
    198 +
    199 +Enabled by default.
    200 +
    201 +==============================================================
    202 +
    203 +mapped:
    204 +
    205 +This is the percentage ram that is filled with mapped pages (applications)
    206 +before the vm will start reclaiming mapped pages by moving them to swap.
    207 +It is altered by the relative stress of the vm at the time so is not
    208 +strictly adhered to to prevent provoking out of memory kills.
    209 +
    210 +Set to 66 by default.
    211 +
    212 +==============================================================
    213 +
    214 max_map_count:
    215
    216 This file contains the maximum number of memory map areas a process