• Eric Dumazet's avatar
    [PATCH] Shrinks sizeof(files_struct) and better layout · 0c9e63fd
    Eric Dumazet authored
    1) Reduce the size of (struct fdtable) to exactly 64 bytes on 32bits
       platforms, lowering kmalloc() allocated space by 50%.
    2) Reduce the size of (files_struct), using a special 32 bits (or
       64bits) embedded_fd_set, instead of a 1024 bits fd_set for the
       close_on_exec_init and open_fds_init fields.  This save some ram (248
       bytes per task) as most tasks dont open more than 32 files.  D-Cache
       footprint for such tasks is also reduced to the minimum.
    3) Reduce size of allocated fdset.  Currently two full pages are
       allocated, that is 32768 bits on x86 for example, and way too much.  The
       minimum is now L1_CACHE_BYTES.
    UP and SMP should benefit from this patch, because most tasks will touch
    only one cache line when open()/close() stdin/stdout/stderr (0/1/2),
    (next_fd, close_on_exec_init, open_fds_init, fd_array[0 ..  2] being in the
    same cache line)
    Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
open.c 26.8 KB