Messages in this thread |  | | | Date | Mon, 23 May 2011 13:01:51 +0200 | | From | Ingo Molnar <> | | Subject | Re: [PATCH 5/9] HWPoison: add memory_failure_queue() |
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* Huang Ying <ying.huang@intel.com> wrote:
> > That's where 'active filters' come into the picture - see my other mail > > (that was in the context of unidentified NMI errors/events) where i > > outlined how they would work in this case and elsewhere. Via active filters > > we could share most of the code, gain access to the events and still have > > kernel driven policy action. > > Is that something as follow? > > - NMI handler run for the hardware error, where hardware error > information is collected and put into perf ring buffer as 'event'.
Correct.
Note that for MCE errors we want the 'persistent event' framework Boris has posted: we want these events to be buffered up to a point even if there is no tool listening in on them:
- this gives us boot-time MCE error coverage
- this protects us against a logging daemon being restarted and events getting lost
> - Some 'active filters' are run for each 'event' in NMI context.
Yeah. Whether it's a human-ASCII space 'filter' or really just a callback you register with that event is secondary - both would work.
> - Some operations can not be done in NMI handler, so they are delayed to > an IRQ handler (can be done with something like irq_work).
Yes.
> - Some other 'active filters' are run for each 'event' in IRQ context. > (For memory error, we can call memory_failure_queue() here).
Correct.
> Where some 'active filters' are kernel built-in, some 'active filters' can be > customized via kernel command line or by user space.
Yes.
> If my understanding as above is correct, I think this is a general and > complex solution. It is a little hard for user to understand which 'active > filters' are in effect. He may need some runtime assistant to understand the > code (maybe /sys/events/active_filters, which list all filters in effect > now), because that is hard only by reading the source code. Anyway, this is > a design style choice.
I don't think it's complex: the built-in rules are in plain sight (can be in the source code or can even be explicitly registered callbacks), the configuration/tooling installed rules will be as complex as the admin or tool wants them to be.
> There are still some issues, I don't know how to solve in above framework. > > - If there are two processes request the same type of hardware error > events. One hardware error event will be copied to two ring buffers (each > for one process), but the 'active filters' should be run only once for each > hardware error event.
With persistent events 'active filters' should only be attached to the central persistent event.
> - How to deal with ring-buffer overflow? For example, there is full of > corrected memory error in ring-buffer, and now a recoverable memory error > occurs but it can not be put into perf ring buffer because of ring-buffer > overflow, how to deal with the recoverable memory error?
The solution is to make it large enough. With *every* queueing solution there will be some sort of queue size limit.
Thanks,
Ingo
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