Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v4] watchdog: Allow nmi watchdog to use "ref-cycles" event | Date | Thu, 8 Jun 2023 18:18:23 +0000 |
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Hi Peter,
> On Jun 2, 2023, at 4:15 PM, Song Liu <songliubraving@meta.com> wrote:
[...]
>>> nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels >>> - Format: [panic,][nopanic,][num] >>> + Format: [panic,][nopanic,][ref-cycles][num] >>> Valid num: 0 or 1 >>> 0 - turn hardlockup detector in nmi_watchdog off >>> 1 - turn hardlockup detector in nmi_watchdog on >>> + ref-cycles - configure the watchdog with perf event >>> + "ref-cycles" instead of "cycles" >>> When panic is specified, panic when an NMI watchdog >>> timeout occurs (or 'nopanic' to not panic on an NMI >>> watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) >> >> I still hate the whole ref-cycles thing, at the very least powerpc also >> has HAVE_HARDLOCKUP_DETECTOR_PERF and they don't have ref-cycles, but >> perhaps them wants to use a different event when the moon is just so... >> >> What again was wrong with the option of specifying a raw event value and >> falling back to cpu-cycles if that fails? > > The same raw event number may mean different events on different hardware. > So it is more likely to make mistakes in configurations. For example, r300 > means ref-cycles on Intel CPUs, but it also means something else on AMD > CPUs. I need to be very careful which hosts to run with nmi_watchdog=r300, > as it may cause surprises. OTOH, nmi_watchdog=ref-cycles won't have this > issue. Of course, this won't work for powerpc.
Does this make sense? Do we have other ideas to configure this?
Thanks, Song
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