On Tue, Jun 19, 2018 at 10:24:44AM +0200, Thomas Hellstrom wrote: > The current Wound-Wait mutex algorithm is actually not Wound-Wait but > Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait > is, contrary to Wait-Die a preemptive algorithm and is known to generate > fewer backoffs. Testing reveals that this is true if the > number of simultaneous contending transactions is small. > As the number of simultaneous contending threads increases, Wait-Wound > becomes inferior to Wait-Die in terms of elapsed time. > Possibly due to the larger number of held locks of sleeping transactions. > > Update documentation and callers. > > Timings using git://people.freedesktop.org/~thomash/ww_mutex_test > tag patch-18-06-15 > > Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly > chosen out of 100000. Four core Intel x86_64: > > Algorithm #threads Rollbacks time > Wound-Wait 4 ~100 ~17s. > Wait-Die 4 ~150000 ~19s. > Wound-Wait 16 ~360000 ~109s. > Wait-Die 16 ~450000 ~82s. > > Cc: Ingo Molnar <[email protected]> > Cc: Jonathan Corbet <[email protected]> > Cc: Gustavo Padovan <[email protected]> > Cc: Maarten Lankhorst <[email protected]> > Cc: Sean Paul <[email protected]> > Cc: David Airlie <[email protected]> > Cc: Davidlohr Bueso <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > Cc: Josh Triplett <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Kate Stewart <[email protected]> > Cc: Philippe Ombredanne <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > Cc: [email protected] > Cc: [email protected] > Cc: [email protected] > Co-authored-by: Peter Zijlstra <[email protected]> > Signed-off-by: Thomas Hellstrom <[email protected]> > > --- > Documentation/locking/ww-mutex-design.txt | 57 +++++++++-- > drivers/dma-buf/reservation.c | 2 +- > drivers/gpu/drm/drm_modeset_lock.c | 2 +- > include/linux/ww_mutex.h | 17 ++- > kernel/locking/locktorture.c | 2 +- > kernel/locking/mutex.c | 165 > +++++++++++++++++++++++++++--- > kernel/locking/test-ww_mutex.c | 2 +- > lib/locking-selftest.c | 2 +- > 8 files changed, 213 insertions(+), 36 deletions(-)
Acked-by: Peter Zijlstra (Intel) <[email protected]> _______________________________________________ dri-devel mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/dri-devel
