• Waiman Long's avatar
    SELinux: Increase ebitmap_node size for 64-bit configuration · a767f680
    Waiman Long authored
    Currently, the ebitmap_node structure has a fixed size of 32 bytes. On
    a 32-bit system, the overhead is 8 bytes, leaving 24 bytes for being
    used as bitmaps. The overhead ratio is 1/4.
    
    On a 64-bit system, the overhead is 16 bytes. Therefore, only 16 bytes
    are left for bitmap purpose and the overhead ratio is 1/2. With a
    3.8.2 kernel, a boot-up operation will cause the ebitmap_get_bit()
    function to be called about 9 million times. The average number of
    ebitmap_node traversal is about 3.7.
    
    This patch increases the size of the ebitmap_node structure to 64
    bytes for 64-bit system to keep the overhead ratio at 1/4. This may
    also improve performance a little bit by making node to node traversal
    less frequent (< 2) as more bits are available in each node.
    Signed-off-by: default avatarWaiman Long <Waiman.Long@hp.com>
    Acked-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
    Signed-off-by: default avatarPaul Moore <pmoore@redhat.com>
    Signed-off-by: default avatarEric Paris <eparis@redhat.com>
    a767f680
ebitmap.h 4.17 KB