linux-kernel - Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK

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Date:   Thu, 19 Oct 2017 13:32:40 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     peterz@...radead.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@....com
Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make
 it not unwind as default

On Wed, Oct 18, 2017 at 12:09:44PM +0200, Ingo Molnar wrote:
> BTW., have you attempted limiting the depth of the stack traces? I suspect more 
> than 2-4 are rarely required to disambiguate the calling context.

I did it for you. Let me show you the result.

1. No lockdep

 Performance counter stats for 'qemu_booting_time.sh bzImage' (10 runs):

       2.756558155 seconds time elapsed                    ( +-  0.09% )

2. Lockdep

 Performance counter stats for 'qemu_booting_time.sh bzImage' (10 runs):

       2.968710420 seconds time elapsed                    ( +-  0.12% )

3. Lockdep + Crossrelease 5 entries

 Performance counter stats for 'qemu_booting_time.sh bzImage' (10 runs):

       3.153839636 seconds time elapsed                    ( +-  0.31% )

4. Lockdep + Crossrelease 3 entries

 Performance counter stats for 'qemu_booting_time.sh bzImage' (10 runs):

       3.137205534 seconds time elapsed                    ( +-  0.87% )

5. Lockdep + Crossrelease + This patch

 Performance counter stats for 'qemu_booting_time.sh bzImage' (10 runs):

       2.963669551 seconds time elapsed                    ( +-  0.11% )

And I will add the result in commit message at the next spin.

Thanks,
Byungchul