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

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Message-ID: <20181002090652.GC116695@gmail.com>
Date:   Tue, 2 Oct 2018 11:06:52 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/5] locking/lockdep: Improve lockdep performance


* Waiman Long <longman@...hat.com> wrote:

> 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.

Impressive speedup!

Mind including the non-lockdep numbers as well, for reference?

Thanks,

	Ingo