linux-kernel - Re: [PATCH v4] watchdog: Allow nmi watchdog to use "ref-cycles" event

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Message-ID: <393545F8-AB12-47F6-9293-75B2274CF7B2@fb.com>
Date:   Fri, 2 Jun 2023 22:11:51 +0000
From:   Song Liu <songliubraving@...a.com>
To:     Song Liu <songliubraving@...a.com>
CC:     Song Liu <song@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Kernel Team <kernel-team@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4] watchdog: Allow nmi watchdog to use "ref-cycles" event

Hi Andrew and Peter, 

Friendly ping... Any comment on this one? 

Thanks,
Song

> On May 25, 2023, at 3:20 PM, Song Liu <songliubraving@...a.com> wrote:
> 
> Hi Andrew and Peter,
> 
> 
>> On May 19, 2023, at 9:59 AM, Song Liu <songliubraving@...a.com> wrote:
>> 
>> Hi Andrew and Peter, 
>> 
>> Does this version look good do you?
>> 
>> Thanks,
>> Song
>> 
>>> On May 17, 2023, at 5:25 PM, Song Liu <song@...nel.org> wrote:
>>> 
>>> NMI watchdog permanently consumes one hardware counters per CPU on the
>>> system. For systems that use many hardware counters, this causes more
>>> aggressive time multiplexing of perf events.
>>> 
>>> OTOH, some CPUs (mostly Intel) support "ref-cycles" event, which is rarely
>>> used. Add kernel cmdline arg nmi_watchdog=ref-cycles to configure the
>>> watchdog to use "ref-cycles" event instead of "cycles".
>>> 
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>> Signed-off-by: Song Liu <song@...nel.org>
> 
> Could you please share your comments on this patch?
> 
> Thanks,
> Song