Hi Vlad, On 03/11/2015 05:54 PM, Vlad Zolotarov wrote: >>>> About the existing RX/TX functions and PPC support: >>>> Note that all of them were created before PPC support for DPDK was >>>> introduced. >>>> At that moment only IA was supported. >>>> That's why in some places where you would expect to see 'mb()' there >>>> are 'volatile' and/or ' rte_compiler_barrier' instead. >>>> Why all that places wasn't updated when PPC support was added - >>>> that's another question. >>>> From my understanding - with current implementation some of DPDK >>>> PMDs RX/TX functions and rte_ring wouldn't work correctly >>> on PPC. >>>> So, I suppose we need to decide for ourselves - do we really want to >>>> support PPC and other architectures with non-IA memory >>> model or not? >>>> If not, then I think we don't need any mb()s inside recv_pkts_lro() >>>> - just rte_compiler_barrier seems enough, and no point to >>> complain about >>>> it in comments. >>>> If yes - then why to introduce a new function with a known potential >>>> bug? >>> In order to introduce a new function with the proper implementation or >>> to fix any other places with the similar weakness I would need a proper >>> tools like a proper platform-dependent barrier-macros similar to >>> smp_Xmb() Linux macros that reduce to a compiler barrier where >>> appropriate or to a proper memory fence where needed. >> I understand that. >> Let's add new macro for that: rte_smp_Xmb() or something, >> so it would be just rte_compiler_barrier() for x86 and a proper mb() >> for PPC. > > There was an idea to use the C11 built-in memory barriers. I suggest we > open a separate discussion about that and add these and the appropriate > fixes in a separate series. There are quite a few places to fix anyway, > which are currently broken on PPC so this patch doesn't make things any > worse. However adding a new memory barrier doesn't belong to an LRO > functionality and thus to this series.
This is an interesting discussion. Just for reference, I submitted a patch on this topic but it was probably too early as only Intel architecture was supported at that time. See http://dpdk.org/ml/archives/dev/2014-May/002597.html Regards, Olivier
