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SubjectRe: [RFCv3 0/9] perf tool: parser generator for events parsing
On Tue, Jan 24, 2012 at 05:26:04PM +0100, Peter Zijlstra wrote:
> On Mon, 2012-01-16 at 13:31 +0100, Jiri Olsa wrote:
> > Here's new version of event parsing patchset. To summarize:
> > - adding event parser bison/flex generator
> > - the event syntax stays as it was
> > - adding event format file sysfs attribute
> > for pmu device
>
> Added Greg to CC, please also see: https://lkml.org/lkml/2012/1/16/148
>
> Right, lets hope we can convince the sysfs people that a few lines are
> ok.. if not we need to find another way to represent all this muck, one
> alternative is exploding the whole thing into a sysfs hierarchy like:
>
>
> format/event: config:0-7
> ...
>
> format/config: config:0-63
> format/config1: config1:0-63
> format/config2: config2:0-63
>
> that will of course consume loads more resources but if that's what it
> takes :-(

Well, what's to keep someone from exploding one of those files to go
over the buffer size without knowing it?

Even after reading the above link, I can't really understand what this
is being used for. As it's sysfs files, why aren't Documentation/ABI/
files also being created with the patch explaining it all?

Again, if at all possible, sysfs should be one value per file. Please
NEVER create a sysfs file that requires a parser to determine what is
going on in it. It should be a simple 'read the value' type thing.

So yes, multiple sysfs files do make sense, the resource load should be
almost non-existant for new ones.

thanks,

greg k-h


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