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Date: Thu, 06 Aug 2020 11:41:06 +0200 From: Thomas Gleixner <tglx@...utronix.de> To: peterz@...radead.org, Valentin Schneider <valentin.schneider@....com> Cc: Vladimir Oltean <olteanv@...il.com>, Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>, Alison Wang <alison.wang@....com>, catalin.marinas@....com, will@...nel.org, paulmck@...nel.org, mw@...ihalf.com, leoyang.li@....com, vladimir.oltean@....com, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Anna-Maria Gleixner <anna-maria@...utronix.de> Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting peterz@...radead.org writes: > On Wed, Aug 05, 2020 at 02:56:49PM +0100, Valentin Schneider wrote: > >> I've been tempted to say the test case is a bit bogus, but am not familiar >> enough with the RT throttling details to stand that ground. That said, from >> both looking at the execution and the stress-ng source code, it seems to >> unconditionally spawn 32 FIFO-50 tasks (there's even an option to make >> these FIFO-99!!!), which is quite a crowd on monoCPU systems. > > Oh, so it's a case of: we do stupid without tuning and the system falls > over. I can live with that. It's not a question of whether you can live with that behaviour for a particular silly test case. The same happens with a single RT runaway task with enough interrupt load on a UP machine. Just validated that. And that has nothing to do with a silly test case. Sporadic runaways due to a bug in a once per week code path simply can happen and having the safety net working depending on a config option selected or not is just wrong. Thanks, tglx
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