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    SubjectRe: [PATCH 00/23] proc cleanup.
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    Date
    Andrew Morton <akpm@osdl.org> writes:

    > ebiederm@xmission.com (Eric W. Biederman) wrote:
    >>
    >> When working on pid namespaces I keep tripping over /proc.
    >> It's hard coded inode numbers and the amount of cruft
    >> accumulated over the years makes it hard to deal with.
    >>
    >> So to put /proc out of my misery here is a series of patches that
    >> removes the worst of the warts.
    >
    > An additional 2.7k of vmlinux. A shame.

    Looks like that at least is compiler dependent, with gcc-3.3.5 I get:

    text data bss dec hex filename
    2601428 502342 226092 3329862 32cf46 ../linux-2.6-ns-mirror-build1/vmlinux
    2602548 502494 226092 3331134 32d43e ../linux-2.6-ns-mirror-build2/vmlinux

    So it looks like 1K of test and about 100 bytes of data.

    Investigating this quickly. Because of the refactoring it
    is hard to pin this down to any major culprit. But that is
    also good news in that it doesn't look like an inline function
    is responsible for this growth :)

    It looks like the culprit for small amounts of growth is
    the work to see if a task still exists, and other similar
    checks that were needed but missing.

    For the big chunks it looks like the work to populate the
    dcache during readdir, which keeps the inode numbers in
    sync and should help readdir+stat performance.

    The other big culprit is proc_flush_task which is both
    more comprehensive and simpler that proc_pid_flush+proc_pid_unhash=107+28.
    But unfortunately that has made it a lot bigger.

    So short of getting better dcache helpers for the case
    where readdir populates the dcache it doesn't look the code
    size will come down much.

    The one practical thing that will help a little is that it
    looks like with just a little more work we can replace
    all of read_lock(&tasklist_lock) with rcu_read_lock().

    add/remove: 33/23 grow/shrink: 28/16 up/down: 4968/-3619 (1349)
    function old new delta
    proc_flush_task - 605 +605
    proc_check_dentry_visible - 325 +325
    proc_fill_cache - 256 +256
    proc_fd_instantiate - 243 +243
    tref_get_by_task - 200 +200
    first_tid - 179 +179
    tgid_base_stuff 336 504 +168
    tid_base_stuff 320 480 +160
    first_tgid - 159 +159
    proc_pident_instantiate - 158 +158
    proc_task_instantiate - 128 +128
    proc_pid_instantiate - 128 +128
    attr_dir_stuff - 120 +120
    proc_attr_dir_operations - 108 +108
    tref_get_by_pid - 107 +107
    proc_task_getattr - 105 +105
    next_tid - 100 +100
    next_tgid - 89 +89
    tref_put - 87 +87
    proc_attr_dir_inode_operations - 84 +84
    do_maps_open - 80 +80
    proc_fd_fill_cache - 63 +63
    proc_task_fill_cache - 60 +60
    proc_pid_fill_cache - 60 +60
    __detach_pid 136 195 +59
    proc_info_read 111 164 +53
    oom_adjust_read 162 215 +53
    proc_get_sb 26 78 +52
    seccomp_write 168 218 +50
    seccomp_read 164 214 +50
    oom_adjust_write 164 214 +50
    proc_pid_attr_read 124 172 +48
    proc_base_stuff - 48 +48
    proc_pid_attr_write 148 194 +46
    proc_fd_link 122 168 +46
    proc_exe_link 152 198 +46
    mounts_open 157 200 +43
    proc_root_link 99 141 +42
    proc_cwd_link 99 141 +42
    tid_fd_revalidate 207 247 +40
    proc_pident_fill_cache - 40 +40
    get_tref_task - 33 +33
    dup_task_struct 137 170 +33
    m_stop 59 88 +29
    m_start 235 264 +29
    tref_reset - 28 +28
    proc_attr_dir_readdir - 28 +28
    proc_pident_readdir 270 296 +26
    proc_attr_dir_lookup - 22 +22
    tref_set - 21 +21
    tref_fini - 21 +21
    tref_init - 18 +18
    proc_pid_follow_link 98 116 +18
    init_tref - 16 +16
    init_task 1328 1344 +16
    pid_revalidate 178 192 +14
    attach_pid 149 162 +13
    tref_get - 8 +8
    mem_read 430 438 +8
    proc_alloc_inode 98 102 +4
    proc_task_readdir 320 323 +3
    pid_delete_dentry 24 21 -3
    m_next 70 61 -9
    proc_readfd 327 307 -20
    copy_process 3190 3170 -20
    smaps_open 43 22 -21
    maps_open 43 22 -21
    proc_tid_attr_lookup 22 - -22
    proc_tgid_attr_lookup 22 - -22
    proc_delete_inode 129 105 -24
    pid_base_dentry_operations 24 - -24
    proc_tid_attr_readdir 28 - -28
    proc_tgid_attr_readdir 28 - -28
    proc_pid_flush 28 - -28
    release_task 257 228 -29
    proc_permission 38 - -38
    proc_pid_make_inode 205 166 -39
    unhash_process 73 33 -40
    de_thread 1310 1266 -44
    proc_check_root 55 - -55
    proc_task_lookup 244 188 -56
    pid_base_iput 62 - -62
    proc_pid_readdir 303 229 -74
    tid_attr_stuff 80 - -80
    tgid_attr_stuff 80 - -80
    proc_task_permission 82 - -82
    proc_tid_attr_inode_operations 84 - -84
    proc_tgid_attr_inode_operations 84 - -84
    proc_mem_inode_operations 84 - -84
    get_tid_list 97 - -97
    proc_pid_unhash 107 - -107
    proc_tid_attr_operations 108 - -108
    proc_tgid_attr_operations 108 - -108
    proc_lookupfd 240 99 -141
    get_tgid_list 146 - -146
    proc_task_root_link 218 - -218
    proc_check_chroot 245 - -245
    switch_exec_pids 290 - -290
    proc_pid_lookup 503 145 -358
    proc_pident_lookup 742 142 -600

    Eric
    -
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