lkml.org 
[lkml]   [2019]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 28/28] locking/lockdep: Reduce lock_list_entries by half
    Date
    The forward and backward dependencies consume the same number of
    list_entries. Since backward dependencies are removed, the max number of
    list_entries can be halved safely: MAX_LOCKDEP_ENTRIES /= 2, which goes
    from 16384 to 8192 or 32768 to 16384.

    Besides memory space reduction, the performance gain is also promising
    with this new IRQ usage checking algorithm. We briefly show the
    performance improvement on a simple workload: Linux kernel build (i.e.,
    make clean; reboot; make vmlinux -j8). It is expected that for complex
    real-world workloads with heavier lock usage and bigger dependency
    graph, the benefits should be more.

    Results:

    ------
    Before
    ------

    direct dependencies: 6900 [max: 32768]
    max bfs queue depth: 272
    find-mask forwards checks: 2875
    find-mask backwards checks: 50229

    -----
    After
    -----

    direct dependencies: 3444 [max: 16384] ( - 50 % )
    max bfs queue depth: 223 ( - 18 % )
    find-mask forwards checks: 370 ( - 87 % )
    find-mask backwards checks: 0 ( - 100 % )

    Signed-off-by: Yuyang Du <duyuyang@gmail.com>
    ---
    kernel/locking/lockdep_internals.h | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
    index 30d021b..3b4b3dd 100644
    --- a/kernel/locking/lockdep_internals.h
    +++ b/kernel/locking/lockdep_internals.h
    @@ -92,11 +92,11 @@ enum {
    * table (if it's not there yet), and we check it for lock order
    * conflicts and deadlocks.
    */
    -#define MAX_LOCKDEP_ENTRIES 16384UL
    +#define MAX_LOCKDEP_ENTRIES 8194UL
    #define MAX_LOCKDEP_CHAINS_BITS 15
    #define MAX_STACK_TRACE_ENTRIES 262144UL
    #else
    -#define MAX_LOCKDEP_ENTRIES 32768UL
    +#define MAX_LOCKDEP_ENTRIES 16384UL

    #define MAX_LOCKDEP_CHAINS_BITS 16

    --
    1.8.3.1
    \
     
     \ /
      Last update: 2019-04-24 12:23    [W:4.145 / U:0.088 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site