Re: 答复: 答复: 答复: [外部邮件] Re: [PATCH] x86/mce: Fix timer interval adjustment after logging a MCE event

[Nikolay Borisov]

On 13.01.26 г. 20:53 ч., Luck, Tony wrote:
> > > The comment in mce_timer_fn says to adjust the polling interval, but
> > > I notice the kernel log always shows an MCE log every 5 minutes. Is this
> > > normal?
> >
> > Use git annotate to figure out which patch added this comment and in context
> > of what and that'll tell you why.
> >
> > As to the 5 minutes, look at how the check interval gets established.
>
> Once upon a time the polling interval started out at 5 minutes, but the
> interval was halved each time an error was found (so interval went
> 150s, 75s, 37s, ... down to 1s). If no error was found, then the interval
> was doubled (going back up to 300s).
>
> This is described in the comment:
>
>          /*
>           * Alert userspace if needed. If we logged an MCE, reduce the polling
>           * interval, otherwise increase the polling interval.
>           */
>
> It seems that the kernel isn't doing that today. Polling at a fixed 300 seconds
> event though errors are being found and logged. Interesting that the timestamps
> are 327.68 seconds apart, rather than 300 and change. So there is some strange
> stuff going on.
>
> I can reproduce here on an Icelake system. Booted with mce=no_cmci to force polling
> (and turned of BIOS firmware first mode).  Injecting an error every 30 seconds I also see
> constant 327 seconds between logs (multiple logs show up because my injection picks memory
> channel "randomly", so there can be several banks with errors when polling happens).
>
> $ dmesg | grep 'Machine Check Event:'
> [  662.632988] EDAC skx MC4: CPU 40: Machine Check Event: 0x0 Bank 13: 0x8c00014200800090
> [  662.727377] EDAC skx MC6: CPU 40: Machine Check Event: 0x0 Bank 21: 0x8c0000c200800090
> [  990.283484] EDAC skx MC4: CPU 121: Machine Check Event: 0x0 Bank 13: 0x8c00010200800090
> [  990.378233] EDAC skx MC6: CPU 121: Machine Check Event: 0x0 Bank 21: 0x8c00014200800090
> [  990.467199] EDAC skx MC0: CPU 3: Machine Check Event: 0x0 Bank 13: 0x8c00004200800090
> [ 1317.939260] EDAC skx MC4: CPU 122: Machine Check Event: 0x0 Bank 13: 0x8c00010200800090
> [ 1318.033721] EDAC skx MC6: CPU 122: Machine Check Event: 0x0 Bank 21: 0x8c00010200800090
> [ 1318.122612] EDAC skx MC0: CPU 14: Machine Check Event: 0x0 Bank 13: 0x8c00004200800090
> [ 1318.211507] EDAC skx MC2: CPU 14: Machine Check Event: 0x0 Bank 21: 0x8c00004200800090
> [ 1645.590773] EDAC skx MC4: CPU 129: Machine Check Event: 0x0 Bank 13: 0x8c00010200800090
> [ 1645.685153] EDAC skx MC6: CPU 129: Machine Check Event: 0x0 Bank 21: 0x8c00018200800090
> [ 1645.773744] EDAC skx MC0: CPU 100: Machine Check Event: 0x0 Bank 13: 0x8c00004200800090
>
> -Tony

At this stage I think lirongqi's patch is ok, but in the long run (i.e 
tomorrow) I will send a patch that simply eliminates mce_notify_irq's 
call in mce_timer_fn. I.e that function should be called only from the 
early notifier.