From: Mark Rutland <mark.rutland@arm.com> To: Doug Anderson <dianders@chromium.org> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Sumit Garg <sumit.garg@linaro.org>, Daniel Thompson <daniel.thompson@linaro.org>, Marc Zyngier <maz@kernel.org>, linux-perf-users@vger.kernel.org, ito-yuichi@fujitsu.com, Chen-Yu Tsai <wens@csie.org>, Ard Biesheuvel <ardb@kernel.org>, Stephen Boyd <swboyd@chromium.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, linux-arm-kernel@lists.infradead.org, kgdb-bugreport@lists.sourceforge.net, Masayoshi Mizuma <msys.mizuma@gmail.com>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Lecopzer Chen <lecopzer.chen@mediatek.com>, Andrey Konovalov <andreyknvl@gmail.com>, Ben Dooks <ben-linux@fluff.org>, Frederic Weisbecker <frederic@kernel.org>, "Gautham R. Shenoy" <gautham.shenoy@amd.com>, Ingo Molnar <mingo@kernel.org>, Jason Wessel <jason.wessel@windriver.com>, Josh Poimboeuf <jpoimboe@kernel.org>, Masahiro Yamada <masahiroy@kernel.org>, Valentin Schneider <vschneid@redhat.com>, Wei Li <liwei391@huawei.com>, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 0/7] arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it Date: Mon, 7 Aug 2023 11:41:24 +0100 [thread overview] Message-ID: <ZNDKVP2m-iiZCz3v@FVFF77S0Q05N.cambridge.arm.com> (raw) In-Reply-To: <CAD=FV=V2fFqwg3f3KS29+AkggHFDbyYvfAb12DrDn_PF8+bJjA@mail.gmail.com> Hi Doug, Apologies for the delay. On Mon, Jul 24, 2023 at 08:55:44AM -0700, Doug Anderson wrote: > On Thu, Jun 1, 2023 at 2:37 PM Douglas Anderson <dianders@chromium.org> wrote: > I'm looking for some ideas on what to do to move this patch series > forward. Thanks to Daniel, the kgdb patch is now in Linus's tree which > hopefully makes this simpler to land. I guess there is still the > irqchip dependency that will need to be sorted out, though... > > Even if folks aren't in agreement about whether this is ready to be > enabled in production, I don't think anything here is super > objectionable or controversial, is it? Can we land it? If you feel > like it needs extra review, would it help if I tried to drum up some > extra people to provide review feedback? Ignoring the soundness issues I mentioned before (which I'm slowly chipping away at, and you're likely lucky enough to avoid in practice)... Having looked over the series, I think the GICv3 bit isn't quite right, but is easy enough to fix. I've commented on the patch with what I think we should have there. The only major thing otherwise from my PoV is the structure of the debug IPI framework. I'm not keen on that being a separate body of code and I think it should live in smp.c along with the other IPIs. I'd also strongly prefer if we could have separate IPI_CPU_BACKTRACE and IPI_CPU_KGDB IPIs, and I think we can do that either by unifying IPI_CPU_STOP && IPI_CPU_CRASH_STOP or by reclaiming IPI_WAKEUP by reusing a different IPI for the parking protocol (e.g. IPI_RESCHEDULE). I think it'd be nice if the series could enable NMIs for backtrace and the CPU_{,CRASH_}STOP cases, with KGDB being the bonus atop. That way it'd be clearly beneficial for anyone trying to debug lockups even if they're not a KGDB user. > Also: in case it's interesting to anyone, I've been doing benchmarks > on sc7180-trogdor devices in preparation for enabling this. On that > platform, I did manage to see about 4% reduction in a set of hackbench > numbers when fully enabling pseudo-NMI. However, when I instead ran > Speedometer 2.1 I saw no difference. See: > > https://issuetracker.google.com/issues/197061987 Thanks for the pointer! I know that there are a couple of things that we could do to slightly improve local_irq_*() when using pNMIs, though I suspect that the bulk of the cost there will come from the necessary synchronization. Thanks, Mark.
WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com> To: Doug Anderson <dianders@chromium.org> Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Sumit Garg <sumit.garg@linaro.org>, Daniel Thompson <daniel.thompson@linaro.org>, Marc Zyngier <maz@kernel.org>, linux-perf-users@vger.kernel.org, ito-yuichi@fujitsu.com, Chen-Yu Tsai <wens@csie.org>, Ard Biesheuvel <ardb@kernel.org>, Stephen Boyd <swboyd@chromium.org>, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>, linux-arm-kernel@lists.infradead.org, kgdb-bugreport@lists.sourceforge.net, Masayoshi Mizuma <msys.mizuma@gmail.com>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Lecopzer Chen <lecopzer.chen@mediatek.com>, Andrey Konovalov <andreyknvl@gmail.com>, Ben Dooks <ben-linux@fluff.org>, Frederic Weisbecker <frederic@kernel.org>, "Gautham R. Shenoy" <gautham.shenoy@amd.com>, Ingo Molnar <mingo@kernel.org>, Jason Wessel <jason.wessel@windriver.com>, Josh Poimboeuf <jpoimboe@kernel.org>, Masahiro Yamada <masahiroy@kernel.org>, Valentin Schneider <vschneid@redhat.com>, Wei Li <liwei391@huawei.com>, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 0/7] arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it Date: Mon, 7 Aug 2023 11:41:24 +0100 [thread overview] Message-ID: <ZNDKVP2m-iiZCz3v@FVFF77S0Q05N.cambridge.arm.com> (raw) In-Reply-To: <CAD=FV=V2fFqwg3f3KS29+AkggHFDbyYvfAb12DrDn_PF8+bJjA@mail.gmail.com> Hi Doug, Apologies for the delay. On Mon, Jul 24, 2023 at 08:55:44AM -0700, Doug Anderson wrote: > On Thu, Jun 1, 2023 at 2:37 PM Douglas Anderson <dianders@chromium.org> wrote: > I'm looking for some ideas on what to do to move this patch series > forward. Thanks to Daniel, the kgdb patch is now in Linus's tree which > hopefully makes this simpler to land. I guess there is still the > irqchip dependency that will need to be sorted out, though... > > Even if folks aren't in agreement about whether this is ready to be > enabled in production, I don't think anything here is super > objectionable or controversial, is it? Can we land it? If you feel > like it needs extra review, would it help if I tried to drum up some > extra people to provide review feedback? Ignoring the soundness issues I mentioned before (which I'm slowly chipping away at, and you're likely lucky enough to avoid in practice)... Having looked over the series, I think the GICv3 bit isn't quite right, but is easy enough to fix. I've commented on the patch with what I think we should have there. The only major thing otherwise from my PoV is the structure of the debug IPI framework. I'm not keen on that being a separate body of code and I think it should live in smp.c along with the other IPIs. I'd also strongly prefer if we could have separate IPI_CPU_BACKTRACE and IPI_CPU_KGDB IPIs, and I think we can do that either by unifying IPI_CPU_STOP && IPI_CPU_CRASH_STOP or by reclaiming IPI_WAKEUP by reusing a different IPI for the parking protocol (e.g. IPI_RESCHEDULE). I think it'd be nice if the series could enable NMIs for backtrace and the CPU_{,CRASH_}STOP cases, with KGDB being the bonus atop. That way it'd be clearly beneficial for anyone trying to debug lockups even if they're not a KGDB user. > Also: in case it's interesting to anyone, I've been doing benchmarks > on sc7180-trogdor devices in preparation for enabling this. On that > platform, I did manage to see about 4% reduction in a set of hackbench > numbers when fully enabling pseudo-NMI. However, when I instead ran > Speedometer 2.1 I saw no difference. See: > > https://issuetracker.google.com/issues/197061987 Thanks for the pointer! I know that there are a couple of things that we could do to slightly improve local_irq_*() when using pNMIs, though I suspect that the bulk of the cost there will come from the necessary synchronization. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-08-07 10:41 UTC|newest] Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-06-01 21:31 [PATCH v9 0/7] arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-06-01 21:31 ` [PATCH v9 1/7] irqchip/gic-v3: Enable support for SGIs to act as NMIs Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 9:50 ` Mark Rutland 2023-08-07 9:50 ` Mark Rutland 2023-08-07 11:22 ` Sumit Garg 2023-08-07 11:22 ` Sumit Garg 2023-08-07 13:25 ` Mark Rutland 2023-08-07 13:25 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 2/7] arm64: idle: Tag the arm64 idle functions as __cpuidle Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 9:52 ` Mark Rutland 2023-08-07 9:52 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 3/7] arm64: Add framework for a debug IPI Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 10:12 ` Mark Rutland 2023-08-07 10:12 ` Mark Rutland 2023-08-21 22:16 ` Doug Anderson 2023-08-21 22:16 ` Doug Anderson 2023-08-22 6:42 ` Mark Rutland 2023-08-22 6:42 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 4/7] arm64: smp: Assign and setup the " Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 10:17 ` Mark Rutland 2023-08-07 10:17 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 5/7] arm64: ipi_debug: Add support for backtrace using " Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 10:23 ` Mark Rutland 2023-08-07 10:23 ` Mark Rutland 2023-08-22 0:06 ` Doug Anderson 2023-08-22 0:06 ` Doug Anderson 2023-08-22 6:35 ` Mark Rutland 2023-08-22 6:35 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 6/7] kgdb: Provide a stub kgdb_nmicallback() if !CONFIG_KGDB Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-06-15 18:14 ` Doug Anderson 2023-06-15 18:14 ` Doug Anderson 2023-06-26 14:30 ` Daniel Thompson 2023-06-26 14:30 ` Daniel Thompson 2023-08-07 10:27 ` Mark Rutland 2023-08-07 10:27 ` Mark Rutland 2023-08-07 10:29 ` Mark Rutland 2023-08-07 10:29 ` Mark Rutland 2023-06-01 21:31 ` [PATCH v9 7/7] arm64: kgdb: Roundup cpus using the debug IPI Douglas Anderson 2023-06-01 21:31 ` Douglas Anderson 2023-08-07 10:28 ` Mark Rutland 2023-08-07 10:28 ` Mark Rutland 2023-08-07 10:47 ` Marc Zyngier 2023-08-07 10:47 ` Marc Zyngier 2023-08-07 10:54 ` Mark Rutland 2023-08-07 10:54 ` Mark Rutland 2023-08-07 11:08 ` Marc Zyngier 2023-08-07 11:08 ` Marc Zyngier 2023-08-07 11:13 ` Mark Rutland 2023-08-07 11:13 ` Mark Rutland 2023-08-07 15:24 ` Daniel Thompson 2023-08-07 15:24 ` Daniel Thompson 2023-08-07 16:04 ` Mark Rutland 2023-08-07 16:04 ` Mark Rutland 2023-08-08 11:17 ` Daniel Thompson 2023-08-08 11:17 ` Daniel Thompson 2023-06-02 5:19 ` [PATCH v9 0/7] arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it Sumit Garg 2023-06-02 5:19 ` Sumit Garg 2023-07-24 15:55 ` Doug Anderson 2023-08-07 10:41 ` Mark Rutland [this message] 2023-08-07 10:41 ` Mark Rutland 2023-08-07 12:46 ` Sumit Garg 2023-08-07 12:46 ` Sumit Garg 2023-08-07 14:43 ` Mark Rutland 2023-08-07 14:43 ` Mark Rutland
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