Re: Hardware Error Kernel Mini-Summit

[Ingo Molnar <mingo@elte.hu>]

* Borislav Petkov <bp@amd64.org> wrote:

> From: "Eric W. Biederman" <ebiederm@xmission.com>
> Date: Tue, May 18, 2010 at 09:14:09PM -0400
> 
> > - Errors that occur frequently. That is broken 
> >   hardware of one time or another.  I want to know 
> >   about that so I can schedule down time to replace my 
> >   memory before I get an uncorrected ECC error.  
> >   Errors of this kind are likely happening frequently 
> >   enough as to impact performance.
> 
> This is exactly the reason why we need a better error 
> logging and reporting than a log.
>
> [ ... lots of specific details snipped ... ]

Basically the idea behind the generic structured logging 
framework (the perf events kernel subsystem) is to have 
both ASCII output (where desired: critical errors), but to 
also have well-specified event format parsable to 
user-space tools.

Plus there's the need for fast, lightweight, flexible 
event passing mechanism - which is given by the perf 
events transport which enables arbitrary size in-memory 
ring-buffers, poll() and epoll support, etc.

perf events supports all these different usecases and 
comes with a (constantly growing) set of events already 
defined upstream. We've got more than a dozen different 
upstream subsystems that have defined events and we have 
over a hundred individual events. There's a rapidly 
growing tool space that makes case by case use of these 
event sources to measure/observe various aspects of the 
system.

Regarding dmesg, there's a WIP patch on lkml that 
integrates printks into this framework as well - makes 
each printk also available as a special string event.

That way a tool can have both programmatic access to 
printk output (without having to interact with the syslog 
buffer itself) - together with all the other structured 
log sources, while humans can also see what is happening.

Thanks,

	Ingo