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    Annotation of /trunk/kernel26-alx/patches-2.6.17-r6/0027-2.6.17-mm-filesize_dependant_lru_cache_add.patch

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    Revision 199 - (hide annotations) (download)
    Fri May 18 11:04:36 2007 UTC (17 years ago) by niro
    File size: 7698 byte(s) 
    -import
    1 niro 199 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     include/linux/sysctl.h | 1
    15     include/linux/writeback.h | 2 +
    16     kernel/sysctl.c | 9 +++++++
    17     mm/filemap.c | 47 +++++++++++++++++++++++++++++++++++--
    18     mm/page-writeback.c | 2 -
    19     mm/swap.c | 3 --
    20     8 files changed, 68 insertions(+), 6 deletions(-)
    21    
    22     Index: linux-ck-dev/include/linux/writeback.h
    23     ===================================================================
    24     --- linux-ck-dev.orig/include/linux/writeback.h 2006-06-18 15:20:10.000000000 +1000
    25     +++ linux-ck-dev/include/linux/writeback.h 2006-06-18 15:25:25.000000000 +1000
    26     @@ -85,6 +85,8 @@ void laptop_io_completion(void);
    27     void laptop_sync_completion(void);
    28     void throttle_vm_writeout(void);
    29    
    30     +extern long total_pages;
    31     +
    32     /* These are exported to sysctl. */
    33     extern int dirty_background_ratio;
    34     extern int vm_dirty_ratio;
    35     Index: linux-ck-dev/mm/filemap.c
    36     ===================================================================
    37     --- linux-ck-dev.orig/mm/filemap.c 2006-06-18 15:20:10.000000000 +1000
    38     +++ linux-ck-dev/mm/filemap.c 2006-06-18 15:25:25.000000000 +1000
    39     @@ -434,6 +434,16 @@ int add_to_page_cache_lru(struct page *p
    40     return ret;
    41     }
    42    
    43     +int add_to_page_cache_lru_tail(struct page *page,
    44     + struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
    45     +{
    46     + int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
    47     +
    48     + if (ret == 0)
    49     + lru_cache_add_tail(page);
    50     + return ret;
    51     +}
    52     +
    53     #ifdef CONFIG_NUMA
    54     struct page *page_cache_alloc(struct address_space *x)
    55     {
    56     @@ -783,6 +793,28 @@ grab_cache_page_nowait(struct address_sp
    57     EXPORT_SYMBOL(grab_cache_page_nowait);
    58    
    59     /*
    60     + * Sysctl which determines whether we should read from large files to the
    61     + * tail of the inactive lru list.
    62     + */
    63     +int vm_tail_largefiles __read_mostly = 1;
    64     +
    65     +/*
    66     + * This examines how large in pages a file size is and returns 1 if it is
    67     + * more than half the unmapped ram. Avoid doing read_page_state which is
    68     + * expensive unless we already know it is likely to be large enough.
    69     + */
    70     +static int large_isize(unsigned long nr_pages)
    71     +{
    72     + if (nr_pages * 6 > total_pages) {
    73     + unsigned long unmapped_ram = total_pages - read_page_state(nr_mapped);
    74     +
    75     + if (nr_pages * 2 > unmapped_ram)
    76     + return 1;
    77     + }
    78     + return 0;
    79     +}
    80     +
    81     +/*
    82     * This is a generic file read routine, and uses the
    83     * mapping->a_ops->readpage() function for the actual low-level
    84     * stuff.
    85     @@ -982,8 +1014,19 @@ no_cached_page:
    86     goto out;
    87     }
    88     }
    89     - error = add_to_page_cache_lru(cached_page, mapping,
    90     - index, GFP_KERNEL);
    91     +
    92     + /*
    93     + * If we know the file is large we add the pages read to the
    94     + * end of the lru as we're unlikely to be able to cache the
    95     + * whole file in ram so make those pages the first to be
    96     + * dropped if not referenced soon.
    97     + */
    98     + if (vm_tail_largefiles && large_isize(end_index))
    99     + error = add_to_page_cache_lru_tail(cached_page,
    100     + mapping, index, GFP_KERNEL);
    101     + else
    102     + error = add_to_page_cache_lru(cached_page, mapping,
    103     + index, GFP_KERNEL);
    104     if (error) {
    105     if (error == -EEXIST)
    106     goto find_page;
    107     Index: linux-ck-dev/mm/page-writeback.c
    108     ===================================================================
    109     --- linux-ck-dev.orig/mm/page-writeback.c 2006-06-18 15:25:22.000000000 +1000
    110     +++ linux-ck-dev/mm/page-writeback.c 2006-06-18 15:25:25.000000000 +1000
    111     @@ -45,7 +45,7 @@
    112     */
    113     static long ratelimit_pages = 32;
    114    
    115     -static long total_pages; /* The total number of pages in the machine. */
    116     +long total_pages __read_mostly; /* The total number of pages in the machine. */
    117     static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */
    118    
    119     /*
    120     Index: linux-ck-dev/mm/swap.c
    121     ===================================================================
    122     --- linux-ck-dev.orig/mm/swap.c 2006-06-18 15:24:48.000000000 +1000
    123     +++ linux-ck-dev/mm/swap.c 2006-06-18 15:25:25.000000000 +1000
    124     @@ -416,8 +416,7 @@ void __pagevec_lru_add_active(struct pag
    125    
    126     /*
    127     * Function used uniquely to put pages back to the lru at the end of the
    128     - * inactive list to preserve the lru order. Currently only used by swap
    129     - * prefetch.
    130     + * inactive list to preserve the lru order.
    131     */
    132     void fastcall lru_cache_add_tail(struct page *page)
    133     {
    134     Index: linux-ck-dev/include/linux/sysctl.h
    135     ===================================================================
    136     --- linux-ck-dev.orig/include/linux/sysctl.h 2006-06-18 15:24:58.000000000 +1000
    137     +++ linux-ck-dev/include/linux/sysctl.h 2006-06-18 15:25:25.000000000 +1000
    138     @@ -191,6 +191,7 @@ enum
    139     VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
    140     VM_SWAP_PREFETCH=33, /* swap prefetch */
    141     VM_HARDMAPLIMIT=34, /* Make mapped a hard limit */
    142     + VM_TAIL_LARGEFILES=35, /* Read large files to lru tail */
    143     };
    144    
    145    
    146     Index: linux-ck-dev/kernel/sysctl.c
    147     ===================================================================
    148     --- linux-ck-dev.orig/kernel/sysctl.c 2006-06-18 15:24:58.000000000 +1000
    149     +++ linux-ck-dev/kernel/sysctl.c 2006-06-18 15:25:25.000000000 +1000
    150     @@ -73,6 +73,7 @@ extern int printk_ratelimit_burst;
    151     extern int pid_max_min, pid_max_max;
    152     extern int sysctl_drop_caches;
    153     extern int percpu_pagelist_fraction;
    154     +extern int vm_tail_largefiles;
    155    
    156     #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
    157     int unknown_nmi_panic;
    158     @@ -809,6 +810,14 @@ static ctl_table vm_table[] = {
    159     .mode = 0644,
    160     .proc_handler = &proc_dointvec,
    161     },
    162     + {
    163     + .ctl_name = VM_TAIL_LARGEFILES,
    164     + .procname = "tail_largefiles",
    165     + .data = &vm_tail_largefiles,
    166     + .maxlen = sizeof(int),
    167     + .mode = 0644,
    168     + .proc_handler = &proc_dointvec,
    169     + },
    170     #ifdef CONFIG_HUGETLB_PAGE
    171     {
    172     .ctl_name = VM_HUGETLB_PAGES,
    173     Index: linux-ck-dev/Documentation/filesystems/proc.txt
    174     ===================================================================
    175     --- linux-ck-dev.orig/Documentation/filesystems/proc.txt 2006-06-18 15:20:10.000000000 +1000
    176     +++ linux-ck-dev/Documentation/filesystems/proc.txt 2006-06-18 15:25:25.000000000 +1000
    177     @@ -1318,6 +1318,14 @@ To free pagecache, dentries and inodes:
    178     As this is a non-destructive operation and dirty objects are not freeable, the
    179     user should run `sync' first.
    180    
    181     +tail_largefiles
    182     +---------------
    183     +
    184     +When enabled reads from large files to the tail end of the inactive lru list.
    185     +This means that any cache from reading large files is dropped very quickly,
    186     +preventing loss of mapped ram and useful pagecache when large files are read.
    187     +This does, however, make caching less effective when working with large files.
    188     +
    189    
    190     2.5 /proc/sys/dev - Device specific parameters
    191     ----------------------------------------------
    192     Index: linux-ck-dev/Documentation/sysctl/vm.txt
    193     ===================================================================
    194     --- linux-ck-dev.orig/Documentation/sysctl/vm.txt 2006-06-18 15:24:58.000000000 +1000
    195     +++ linux-ck-dev/Documentation/sysctl/vm.txt 2006-06-18 15:25:25.000000000 +1000
    196     @@ -37,7 +37,7 @@ Currently, these files are in /proc/sys/
    197    
    198     dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
    199     dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
    200     -block_dump, swap_token_timeout, drop-caches:
    201     +block_dump, swap_token_timeout, drop-caches, tail_largefiles:
    202    
    203     See Documentation/filesystems/proc.txt
    204