[PATCH] powerpc: fix sysconf support for cache geometries

[Richard Henderson]

On 06/15/2017 04:53 PM, Paul Clarke wrote:
> On 06/15/2017 04:03 PM, Richard Henderson wrote:
>> On 06/15/2017 01:45 PM, Paul Clarke wrote:
>> Any thoughts on falling back to AT_*CACHEBSIZE for _SC_LEVEL1_*CACHE_LINESIZE
>> for older kernels where AT_L1*_CACHEGEOMETRY is not present?
> 
> Ben'll tell you (as he told me ;-) that those aren't the same thing.  The
> former, "CACHEBSIZE", is the cache block size, which is the unit size for
> cache operations (e.g. "Cache Block Touch", "Cache Block Clear", etc.).  The
> latter, "CACHE_LINESIZE", is, well, the cache line size (with respect to
> associativity, etc.).
Yeah, yeah, but... show me where it's different, for L1, in practice.

> Did you want to respin your sysconf patch? I notice you also included L4,
which always returns 0, a value, unlike my patch, which will fail (return -1,
EINVAL). Yours may be preferred in that regard, since the "names" for the L4
queries are not completely unknown.

-1 without EINVAL is, afaik, an indication that L4 does not exist.
Whereas 0 indicates that we don't know.

That said, I really don't care about the deep cache hierarchy, so I'm fine with 
either as a result.


r~