linux-kernel - [PATCH 0/5] locking/lockdep: Improve lockdep performance

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Date:   Fri, 28 Sep 2018 13:53:16 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, Waiman Long <longman@...hat.com>
Subject: [PATCH 0/5] locking/lockdep: Improve lockdep performance

Enabling CONFIG_LOCKDEP and other related debug options will greatly
reduce system performance. This patchset aims to reduce the performance
slowdown caused by the lockdep code.

Patch 1 just removes an inline function that wasn't used.

Patches 2 and 3 are minor twists to optimize the code.

Patch 4 makes class->ops a per-cpu counter.

Patch 5 moves the lock_release() call outside of a lock critical section.

Parallel kernel compilation tests (make -j <#cpu>) were performed on
2 different systems:

 1) an 1-socket 22-core 44-thread Skylake system
 2) a 4-socket 72-core 144-thread Broadwell system

The build times with pre-patch and post-patch debug kernels were:

   System      Pre-patch     Post-patch    %Change
   ------      ---------     ----------    -------
  1-socket      8m53.9s        8m41.2s      -2.4%
  4-socket      7m27.0s        5m31.0s      -26%

I think it is the last 2 patches that yield most of the performance
improvement.

Waiman Long (5):
  locking/lockdep: Remove add_chain_cache_classes()
  locking/lockdep: Eliminate redundant irqs check in __lock_acquire()
  locking/lockdep: Add a faster path in __lock_release()
  locking/lockdep: Make class->ops a percpu counter
  locking/lockdep: Call lock_release after releasing the lock

 include/linux/lockdep.h          |   2 +-
 include/linux/rwlock_api_smp.h   |  16 +++---
 include/linux/spinlock_api_smp.h |   8 +--
 kernel/locking/lockdep.c         | 120 ++++++++++++---------------------------
 4 files changed, 48 insertions(+), 98 deletions(-)

-- 
1.8.3.1