[dpdk-dev] [PATCH v2] ring: use aligned memzone allocation

[Verkamp, Daniel]

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Saturday, June 3, 2017 3:00 AM
> To: Verkamp, Daniel <daniel.verkamp at intel.com>; dev at dpdk.org
> Cc: Richardson, Bruce <bruce.richardson at intel.com>
> Subject: RE: [dpdk-dev] [PATCH v2] ring: use aligned memzone allocation
> 
> 
> 
> >
> > The PROD/CONS_ALIGN values on x86-64 are set to 2 cache lines, so members
> of struct rte_ring are 128 byte aligned,
> >and therefore the whole struct needs 128-byte alignment according to the ABI
> so that the 128-byte alignment of the fields can be guaranteed.
> 
> Ah ok, missed the fact that rte_ring is 128B aligned these days.
> BTW, I probably missed the initial discussion, but what was the reason for that?
> Konstantin

I don't know why PROD_ALIGN/CONS_ALIGN use 128 byte alignment; it seems unnecessary if the cache line is only 64 bytes.  An alternate fix would be to just use cache line alignment for these fields (since memzones are already cache line aligned).  Maybe there is some deeper reason for the >= 128-byte alignment logic in rte_ring.h?

Thanks,
-- Daniel