Hi Morten,
> > Most of the fast path ring library functions access the two cache lines > > containing > > respectively the r->prod and r->cons structures. > > > > Some of the fast path functions also have to fetch r->capacity and r->mask, > > which reside in another cache line. > > > > What do you think about adding shadow variables of r->capacity and r->mask > > to the same cache line as r->prod, to improve ring library performance (by > > avoiding having to read a third cache line) when under CPU cache pressure? > Agree with the idea. I am not sure about the performance as these are > read-only data. IMO, we should not worry about it as it saves > one cache line (but we do not need to measure the performance). They will > occupy 12B, but I do not see how we will occupy the > entire 64B of the cacheline in the near future. > > Also, the shadow variables need to be part of both r->prod and r->cons. Personally, I think that for majority of cases the perf gain with be either tiny or none. >From other side, I don't see any harm with that approach, as Honnapa said, we do should have space for that in prod/cons cache-lines. So, no objections from me in general. Thanks Konstantin
