<snip> > > > From: Mattias Rönnblom [mailto:hof...@lysator.liu.se] > > Sent: Wednesday, 10 August 2022 13.56 > > > > On 2022-08-09 17:26, Stephen Hemminger wrote: > > [...] > > > > > Alignment seems like a non-issue to me. A NT-store memcpy() can be > > made free of alignment requirements, incurring only a very slight cost > > for the always-aligned case (who has their data always 16-byte aligned > > anyways?). > > > > The memory barrier required on x86 seems like a bigger issue. > > > > > Maybe rte_non_cache_copy()? > > > > > > > rte_memcpy_nt_weakly_ordered(), or rte_memcpy_nt_weak(). And a > > rte_memcpy_nt() with the sfence is place, which the user hopefully > > will find first? I don't know. I would prefer not having the weak > > variant at all. I think providing weakly ordered version is required to offset the cost of the barriers. One might be able to copy multiple packets and then issue a barrier.
> > > > Accepting weak memory ordering (i.e., no sfence) could also be one of > > the flags, assuming rte_memcpy_nt() would have a flags parameter. > > Default is safe (=memcpy() semantics), but potentially slower. > > Excellent idea! > > > > > > Want to avoid the naive user just doing s/memcpy/rte_memcpy_nt/ and > > expect > > > everything to work.
