From: Byungchul Park <byungchul.park@lge.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: peterz@infradead.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-team@lge.com,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default
Date: Thu, 19 Oct 2017 15:22:55 +0900 [thread overview]
Message-ID: <20171019062255.GC3310@X58A-UD3R> (raw)
In-Reply-To: <20171019061112.GB3310@X58A-UD3R>
On Thu, Oct 19, 2017 at 03:11:12PM +0900, Byungchul Park wrote:
> On Thu, Oct 19, 2017 at 07:57:30AM +0200, Ingo Molnar wrote:
> >
> > * 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?
>
> Ah, the last version of crossrelease merged into vanilla, records 5
> entries, since I thought it overloads too much if full stack is used,
> and 5 entries are enough. Don't you think so?
>
> > 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
>
> BTW, is there any crash by cross-release I don't know? Of course, I know
> cases of false positives, but I don't about crash.
Are you talking about the oops by 'null pointer dereference' by unwinder a
few weeks ago?
At the time, cross-release was falsely accused. AFAIK, cross-release has
not crashed system yet.
WARNING: multiple messages have this Message-ID (diff)
From: Byungchul Park <byungchul.park@lge.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: peterz@infradead.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-team@lge.com,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default
Date: Thu, 19 Oct 2017 15:22:55 +0900 [thread overview]
Message-ID: <20171019062255.GC3310@X58A-UD3R> (raw)
In-Reply-To: <20171019061112.GB3310@X58A-UD3R>
On Thu, Oct 19, 2017 at 03:11:12PM +0900, Byungchul Park wrote:
> On Thu, Oct 19, 2017 at 07:57:30AM +0200, Ingo Molnar wrote:
> >
> > * 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?
>
> Ah, the last version of crossrelease merged into vanilla, records 5
> entries, since I thought it overloads too much if full stack is used,
> and 5 entries are enough. Don't you think so?
>
> > 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
>
> BTW, is there any crash by cross-release I don't know? Of course, I know
> cases of false positives, but I don't about crash.
Are you talking about the oops by 'null pointer dereference' by unwinder a
few weeks ago?
At the time, cross-release was falsely accused. AFAIK, cross-release has
not crashed system yet.
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next prev parent reply other threads:[~2017-10-19 6:23 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-18 9:13 [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Byungchul Park
2017-10-18 9:13 ` Byungchul Park
2017-10-18 9:13 ` [PATCH 2/2] lockdep: Remove BROKEN flag of LOCKDEP_CROSSRELEASE Byungchul Park
2017-10-18 9:13 ` Byungchul Park
2017-10-18 10:12 ` Ingo Molnar
2017-10-18 10:12 ` Ingo Molnar
2017-10-19 1:58 ` Byungchul Park
2017-10-19 1:58 ` Byungchul Park
2017-10-18 10:09 ` [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Ingo Molnar
2017-10-18 10:09 ` Ingo Molnar
2017-10-19 4:32 ` Byungchul Park
2017-10-19 4:32 ` Byungchul Park
2017-10-19 5:57 ` Ingo Molnar
2017-10-19 5:57 ` Ingo Molnar
2017-10-19 6:11 ` Byungchul Park
2017-10-19 6:11 ` Byungchul Park
2017-10-19 6:22 ` Ingo Molnar
2017-10-19 6:22 ` Ingo Molnar
2017-10-19 6:36 ` Byungchul Park
2017-10-19 6:36 ` Byungchul Park
2017-10-19 8:05 ` Ingo Molnar
2017-10-19 8:05 ` Ingo Molnar
2017-10-19 6:22 ` Byungchul Park [this message]
2017-10-19 6:22 ` Byungchul Park
2017-10-19 8:10 ` Ingo Molnar
2017-10-19 8:10 ` Ingo Molnar
2017-10-19 9:02 ` 박병철/선임연구원/SW Platform(연)AOT팀(byungchul.park@lge.com)
2017-10-19 9:02 ` 박병철/선임연구원/SW Platform(연)AOT팀(byungchul.park@lge.com)
2017-10-19 9:41 ` Ingo Molnar
2017-10-19 9:41 ` Ingo Molnar
2017-10-18 13:23 ` Thomas Gleixner
2017-10-18 13:23 ` Thomas Gleixner
2017-10-18 13:30 ` Ingo Molnar
2017-10-18 13:30 ` Ingo Molnar
2017-10-18 13:36 ` Thomas Gleixner
2017-10-18 13:36 ` Thomas Gleixner
2017-10-18 14:15 ` Matthew Wilcox
2017-10-18 14:15 ` Matthew Wilcox
2017-10-18 14:35 ` Thomas Gleixner
2017-10-18 14:35 ` Thomas Gleixner
2017-10-18 17:05 ` Ingo Molnar
2017-10-18 17:05 ` Ingo Molnar
2017-10-19 2:00 ` Byungchul Park
2017-10-19 2:00 ` Byungchul Park
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