On Thu, Sep 13, 2018 at 05:47:29PM +0800, Jason Wang wrote: > > > On 2018年09月13日 16:59, Tiwei Bie wrote: > > > If what you say is true then we should take a careful look > > > and not supporting these generic things with packed layout. > > > Once we do support them it will be too late and we won't > > > be able to get performance back. > > I think it's a good point that we don't need to support > > everything in packed ring (especially these which would > > hurt the performance), as the packed ring aims at high > > performance. I'm also wondering about the features. Is > > there any possibility that we won't support the out of > > order processing (at least not by default) in packed ring? > > If I didn't miss anything, the need to support out of order > > processing in packed ring will make the data structure > > inside the driver not cache friendly which is similar to > > the case of the descriptor table in the split ring (the > > difference is that, it only happens in driver now). > > Out of order is not the only user, DMA is another one. We don't have used > ring(len), so we need to maintain buffer length somewhere even for in order > device. For a bunch of systems dma unmap is a nop so we do not really need to maintain it. It's a question of an API to detect that and optimize for it. I posted a proposed patch for that - want to try using that? > But if it's not too late, I second for a OUT_OF_ORDER feature. > Starting from in order can have much simpler code in driver. > > Thanks It's tricky to change the flag polarity because of compatibility with legacy interfaces. Why is this such a big deal? Let's teach drivers about IN_ORDER, then if devices are in order it will get enabled by default. -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
