On 03/09/2019 08:31, Ming Lei wrote: > Hi Daniel, > > On Tue, Sep 03, 2019 at 07:59:39AM +0200, Daniel Lezcano wrote: >> >> Hi Ming Lei, >> >> On 03/09/2019 05:30, Ming Lei wrote: >> >> [ ... ] >> >> >>>>> 2) irq/timing doesn't cover softirq >>>> >>>> That's solvable, right? >>> >>> Yeah, we can extend irq/timing, but ugly for irq/timing, since irq/timing >>> focuses on hardirq predication, and softirq isn't involved in that >>> purpose. >>> >>>> >>>>> Daniel, could you take a look and see if irq flood detection can be >>>>> implemented easily by irq/timing.c? >>>> >>>> I assume you can take a look as well, right? >>> >>> Yeah, I have looked at the code for a while, but I think that irq/timing >>> could become complicated unnecessarily for covering irq flood detection, >>> meantime it is much less efficient for detecting IRQ flood. >> >> In the series, there is nothing describing rigorously the problem (I can >> only guess) and why the proposed solution solves it. >> >> What is your definition of an 'irq flood'? A high irq load? An irq >> arriving while we are processing the previous one in the bottom halves? > > So far, it means that handling interrupt & softirq takes all utilization > of one CPU, then processes can't be run on this CPU basically, usually > sort of CPU lockup warning will be triggered. It is a scheduler problem then ? >> The patch 2/4 description says "however IO completion is only done on >> one of these submission CPU cores". That describes the bottleneck and >> then the patch says "Add IRQF_RESCUE_THREAD to create one interrupt >> thread handler", what is the rational between the bottleneck (problem) >> and the irqf_rescue_thread (solution)? > > The solution is to switch to handle this interrupt on the created rescue > irq thread context when irq flood is detected, and 'this interrupt' means > the interrupt requested with IRQF_RESCUE_THREAD. > >> >> Is it really the solution to track the irq timings to detect a flood? > > The solution tracks the time taken on running do_IRQ() for each CPU. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
