Re: [PATCH 1/2] tools, perf: Add a precise event qualifier v2

[Andi Kleen <andi@firstfloor.org>]

> Your feature to export 'precise' requirements on events looks useful to 
> me. We could implement it not by special casing it implicitly but by 
> saying that if ../format/precise contains something like:
> 
>    attr:240-241
> 
> then that's a natural extension of the config:X-Y format and should be 
> interpreted to mean mean 2 bits in the perf attr field. I.e. we could go 
> beyond the config bitfield.
> 
> Basically the whole perf_event_attr can be thought of as a 'giant 
> bitfield', in which we can specify values to export an enumerated list of 
> events from the kernel to tooling.
> 
> (Using attr:X-Y the config and config1 variants can be expressed as well, 
> as the config fields are inside the attr structure.)
> 
> The positions within the perf_attr are an ABI, so this would work pretty 
> well.

Wouldn't we need different bits for each architecture then?
32bit/64bit, some archs with weird alignment rules, maybe different for
BE/LE too?

Ok I suppose it could be somehow auto generated in asm-offsets.c,
although I'm not sure how to get a bitfield offset there.

-Andi


-- 
ak@linux.intel.com -- Speaking for myself only.