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author | Waiman Long <longman@redhat.com> | 2017-08-14 16:07:02 -0400 |
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committer | Ingo Molnar <mingo@kernel.org> | 2017-08-29 15:14:38 +0200 |
commit | 34d54f3d6917f519693dbe873ee59cd06fb515ed (patch) | |
tree | 741e660fcb817109ba014b270315cc150d9a9e7c /kernel/ucount.c | |
parent | 966a967116e699762dbf4af7f9e0d1955c25aa37 (diff) | |
download | op-kernel-dev-34d54f3d6917f519693dbe873ee59cd06fb515ed.zip op-kernel-dev-34d54f3d6917f519693dbe873ee59cd06fb515ed.tar.gz |
locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
All the locking related cmpxchg's in the following functions are
replaced with the _acquire variants:
- pv_queued_spin_steal_lock()
- trylock_clear_pending()
This change should help performance on architectures that use LL/SC.
The cmpxchg in pv_kick_node() is replaced with a relaxed version
with explicit memory barrier to make sure that it is fully ordered
in the writing of next->lock and the reading of pn->state whether
the cmpxchg is a success or failure without affecting performance in
non-LL/SC architectures.
On a 2-socket 12-core 96-thread Power8 system with pvqspinlock
explicitly enabled, the performance of a locking microbenchmark
with and without this patch on a 4.13-rc4 kernel with Xinhui's PPC
qspinlock patch were as follows:
# of thread w/o patch with patch % Change
----------- --------- ---------- --------
8 5054.8 Mop/s 5209.4 Mop/s +3.1%
16 3985.0 Mop/s 4015.0 Mop/s +0.8%
32 2378.2 Mop/s 2396.0 Mop/s +0.7%
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1502741222-24360-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/ucount.c')
0 files changed, 0 insertions, 0 deletions