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    Contents of /trunk/kernel26-alx/patches-2.6.21-r13/0017-2.6.21-mm-filesize_dependant_lru_cache_add.patch

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    Revision 445 - (show annotations) (download)
    Tue Jan 15 00:44:37 2008 UTC (16 years, 3 months ago) by niro
    File size: 6028 byte(s) 
    -added patches for 2.6.21-alx-r13
    1 When reading from large files through the generic file read functions into
    2 page cache we can detect when a file is so large that it is unlikely to be
    3 fully cached in ram.
    4
    5 Add a tunable /proc/sys/vm/tail_largefiles that puts them at the tail of the
    6 inactive list to minimise their harm on present mapped pages and pagecache
    7 and enable it by default.
    8
    9 Signed-off-by: Con Kolivas <kernel@kolivas.org>
    10
    11 ---
    12 Documentation/filesystems/proc.txt | 8 +++++
    13 Documentation/sysctl/vm.txt | 2 -
    14 kernel/sysctl.c | 9 ++++++
    15 mm/filemap.c | 53 +++++++++++++++++++++++++++++++++++--
    16 mm/swap.c | 3 --
    17 5 files changed, 70 insertions(+), 5 deletions(-)
    18
    19 Index: linux-2.6.21-ck2/mm/filemap.c
    20 ===================================================================
    21 --- linux-2.6.21-ck2.orig/mm/filemap.c 2007-05-14 19:49:18.000000000 +1000
    22 +++ linux-2.6.21-ck2/mm/filemap.c 2007-05-14 19:49:56.000000000 +1000
    23 @@ -466,6 +466,16 @@ int add_to_page_cache_lru(struct page *p
    24 return ret;
    25 }
    26
    27 +int add_to_page_cache_lru_tail(struct page *page,
    28 + struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
    29 +{
    30 + int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
    31 +
    32 + if (ret == 0)
    33 + lru_cache_add_tail(page);
    34 + return ret;
    35 +}
    36 +
    37 #ifdef CONFIG_NUMA
    38 struct page *__page_cache_alloc(gfp_t gfp)
    39 {
    40 @@ -836,6 +846,34 @@ static void shrink_readahead_size_eio(st
    41 ra->ra_pages /= 4;
    42 }
    43
    44 +/*
    45 + * Sysctl which determines whether we should read from large files to the
    46 + * tail of the inactive lru list.
    47 + */
    48 +int vm_tail_largefiles __read_mostly = 1;
    49 +
    50 +static inline int nr_mapped(void)
    51 +{
    52 + return global_page_state(NR_FILE_MAPPED) +
    53 + global_page_state(NR_ANON_PAGES);
    54 +}
    55 +
    56 +/*
    57 + * This examines how large in pages a file size is and returns 1 if it is
    58 + * more than half the unmapped ram. Avoid doing read_page_state which is
    59 + * expensive unless we already know it is likely to be large enough.
    60 + */
    61 +static int large_isize(unsigned long nr_pages)
    62 +{
    63 + if (nr_pages * 6 > vm_total_pages) {
    64 + unsigned long unmapped_ram = vm_total_pages - nr_mapped();
    65 +
    66 + if (nr_pages * 2 > unmapped_ram)
    67 + return 1;
    68 + }
    69 + return 0;
    70 +}
    71 +
    72 /**
    73 * do_generic_mapping_read - generic file read routine
    74 * @mapping: address_space to be read
    75 @@ -1044,8 +1082,19 @@ no_cached_page:
    76 goto out;
    77 }
    78 }
    79 - error = add_to_page_cache_lru(cached_page, mapping,
    80 - index, GFP_KERNEL);
    81 +
    82 + /*
    83 + * If we know the file is large we add the pages read to the
    84 + * end of the lru as we're unlikely to be able to cache the
    85 + * whole file in ram so make those pages the first to be
    86 + * dropped if not referenced soon.
    87 + */
    88 + if (vm_tail_largefiles && large_isize(end_index))
    89 + error = add_to_page_cache_lru_tail(cached_page,
    90 + mapping, index, GFP_KERNEL);
    91 + else
    92 + error = add_to_page_cache_lru(cached_page, mapping,
    93 + index, GFP_KERNEL);
    94 if (error) {
    95 if (error == -EEXIST)
    96 goto find_page;
    97 Index: linux-2.6.21-ck2/mm/swap.c
    98 ===================================================================
    99 --- linux-2.6.21-ck2.orig/mm/swap.c 2007-05-14 19:49:55.000000000 +1000
    100 +++ linux-2.6.21-ck2/mm/swap.c 2007-05-14 19:49:56.000000000 +1000
    101 @@ -434,8 +434,7 @@ void __pagevec_lru_add_active(struct pag
    102
    103 /*
    104 * Function used uniquely to put pages back to the lru at the end of the
    105 - * inactive list to preserve the lru order. Currently only used by swap
    106 - * prefetch.
    107 + * inactive list to preserve the lru order.
    108 */
    109 void fastcall lru_cache_add_tail(struct page *page)
    110 {
    111 Index: linux-2.6.21-ck2/kernel/sysctl.c
    112 ===================================================================
    113 --- linux-2.6.21-ck2.orig/kernel/sysctl.c 2007-05-14 19:49:55.000000000 +1000
    114 +++ linux-2.6.21-ck2/kernel/sysctl.c 2007-05-14 19:49:56.000000000 +1000
    115 @@ -71,6 +71,7 @@ extern int suid_dumpable;
    116 extern char core_pattern[];
    117 extern int pid_max;
    118 extern int min_free_kbytes;
    119 +extern int vm_tail_largefiles;
    120 extern int printk_ratelimit_jiffies;
    121 extern int printk_ratelimit_burst;
    122 extern int pid_max_min, pid_max_max;
    123 @@ -759,6 +760,14 @@ static ctl_table vm_table[] = {
    124 .mode = 0644,
    125 .proc_handler = &proc_dointvec,
    126 },
    127 + {
    128 + .ctl_name = CTL_UNNUMBERED,
    129 + .procname = "tail_largefiles",
    130 + .data = &vm_tail_largefiles,
    131 + .maxlen = sizeof(int),
    132 + .mode = 0644,
    133 + .proc_handler = &proc_dointvec,
    134 + },
    135 #ifdef CONFIG_HUGETLB_PAGE
    136 {
    137 .ctl_name = VM_HUGETLB_PAGES,
    138 Index: linux-2.6.21-ck2/Documentation/filesystems/proc.txt
    139 ===================================================================
    140 --- linux-2.6.21-ck2.orig/Documentation/filesystems/proc.txt 2007-05-14 19:49:18.000000000 +1000
    141 +++ linux-2.6.21-ck2/Documentation/filesystems/proc.txt 2007-05-14 19:49:56.000000000 +1000
    142 @@ -1325,6 +1325,14 @@ To free pagecache, dentries and inodes:
    143 As this is a non-destructive operation and dirty objects are not freeable, the
    144 user should run `sync' first.
    145
    146 +tail_largefiles
    147 +---------------
    148 +
    149 +When enabled reads from large files to the tail end of the inactive lru list.
    150 +This means that any cache from reading large files is dropped very quickly,
    151 +preventing loss of mapped ram and useful pagecache when large files are read.
    152 +This does, however, make caching less effective when working with large files.
    153 +
    154
    155 2.5 /proc/sys/dev - Device specific parameters
    156 ----------------------------------------------
    157 Index: linux-2.6.21-ck2/Documentation/sysctl/vm.txt
    158 ===================================================================
    159 --- linux-2.6.21-ck2.orig/Documentation/sysctl/vm.txt 2007-05-14 19:49:55.000000000 +1000
    160 +++ linux-2.6.21-ck2/Documentation/sysctl/vm.txt 2007-05-14 19:49:56.000000000 +1000
    161 @@ -39,7 +39,7 @@ Currently, these files are in /proc/sys/
    162
    163 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
    164 dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
    165 -block_dump, swap_token_timeout, drop-caches:
    166 +block_dump, swap_token_timeout, drop-caches, tail_largefiles:
    167
    168 See Documentation/filesystems/proc.txt
    169