Eric Dumazet <eric.dumazet@xxxxxxxxx> writes: > On Wed, 2013-11-13 at 15:10 +0800, Jason Wang wrote: > >> There's one concern with EWMA. How well does it handle multiple streams >> each with different packet size? E.g there may be two flows, one with >> 256 bytes each packet another is 64K. Looks like it can result we >> allocate PAGE_SIZE buffer for 256 (which is bad since the >> payload/truesize is low) bytes or 1500+ for 64K buffer (which is ok >> since we can do coalescing). > > It's hard to predict the future ;) > > 256 bytes frames consume 2.5 KB anyway on a traditional NIC. > If it was a concern, we would have it already. > > If you receive a mix of big and small frames, there is no win. Well, that's not quite true. The device could optimistically look through the queue a bit for a small buffer; it does not need to consume in order. We'd probably want a feature bit for this. I look forward to your thoughts on what mixing algorithm of different sizes to use, of course. Meanwhile, I suspect your patch works well because of 4k pages. 80% non-GSO packets won't drop the average len below 4k. On PPC64 with 64k pages, that's not true. I wonder if "last used len" would work about as well; it really might if we had a smarter device... Cheers, Rusty. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
