Messages in this thread | | | Date | Thu, 19 Oct 2017 07:57:30 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default |
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* Byungchul Park <byungchul.park@lge.com> wrote:
> 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: 2.756558155 seconds time elapsed ( +- 0.09% ) > 2. Lockdep: 2.968710420 seconds time elapsed ( +- 0.12% ) > 3. Lockdep + Crossrelease 5 entries: 3.153839636 seconds time elapsed ( +- 0.31% ) > 4. Lockdep + Crossrelease 3 entries: 3.137205534 seconds time elapsed ( +- 0.87% ) > 5. Lockdep + Crossrelease + This patch: 2.963669551 seconds time elapsed ( +- 0.11% )
I think the lockdep + crossrelease + full-stack numbers are missing?
But yeah, looks like single-entry-stacktrace crossrelease only has a +0.2% performance cost (with 0.1% noise), while lockdep itself has a +7.7% cost.
That's very reasonable and we can keep the single-entry cross-release feature enabled by default as part of CONFIG_PROVE_LOCKING=y - assuming all the crashes and false positives are fixed by the next merge window.
Thanks,
Ingo
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