On Mon, Oct 03, 2022 at 12:11:39AM +0000, Bobby Eshleman wrote: > On Thu, Oct 06, 2022 at 09:34:10AM +0200, Stefano Garzarella wrote: > > On Thu, Oct 06, 2022 at 03:08:12AM -0400, Michael S. Tsirkin wrote: > > > On Wed, Oct 05, 2022 at 06:19:44PM -0700, Bobby Eshleman wrote: > > > > This patch replaces the struct virtio_vsock_pkt with struct sk_buff. > > > > > > > > Using sk_buff in vsock benefits it by a) allowing vsock to be extended > > > > for socket-related features like sockmap, b) vsock may in the future > > > > use other sk_buff-dependent kernel capabilities, and c) vsock shares > > > > commonality with other socket types. > > > > > > > > This patch is taken from the original series found here: > > > > https://lore.kernel.org/all/cover.1660362668.git.bobby.eshleman@xxxxxxxxxxxxx/ > > > > > > > > Small-sized packet throughput improved by ~5% (from 18.53 Mb/s to 19.51 > > > > Mb/s). Tested using uperf, 16B payloads, 64 threads, 100s, averaged from > > > > 10 test runs (n=10). This improvement is likely due to packet merging. > > > > > > > > Large-sized packet throughput decreases ~9% (from 27.25 Gb/s to 25.04 > > > > Gb/s). Tested using uperf, 64KB payloads, 64 threads, 100s, averaged > > > > from 10 test runs (n=10). > > > > > > > > Medium-sized packet throughput decreases ~5% (from 4.0 Gb/s to 3.81 > > > > Gb/s). Tested using uperf, 4k to 8k payload sizes picked randomly > > > > according to normal distribution, 64 threads, 100s, averaged from 10 > > > > test runs (n=10). > > > > > > It is surprizing to me that the original vsock code managed to outperform > > > the new one, given that to my knowledge we did not focus on optimizing it. > > > > Yeah mee to. > > > > Indeed. > > > From this numbers maybe the allocation cost has been reduced as it performs > > better with small packets. But with medium to large packets we perform > > worse, perhaps because previously we were allocating a contiguous buffer up > > to 64k? > > Instead alloc_skb() could allocate non-contiguous pages ? (which would solve > > the problems we saw a few days ago) > > > > I think this would be the case with alloc_skb_with_frags(), but > internally alloc_skb() uses kmalloc() for the payload and sk_buff_head > slab allocations for the sk_buff itself (all the more confusing to me, > as the prior allocator also uses two separate allocations per packet). I think it is related to your implementation of virtio_transport_add_to_queue(), where you introduced much more complicated logic than before: - spin_lock_bh(&vsock->send_pkt_list_lock); - list_add_tail(&pkt->list, &vsock->send_pkt_list); - spin_unlock_bh(&vsock->send_pkt_list_lock); - + virtio_transport_add_to_queue(&vsock->send_pkt_queue, skb); A simple list_add_tail() is definitely faster than your virtio_transport_skbs_can_merge() check. So, why do you have to merge skb while we don't merge virtio_vsock_pkt? _If_ you are trying to mimic TCP, I think you are doing it wrong, it can be much more efficient if you could do the merge in sendmsg() before skb is even allocated, see tcp_sendmsg_locked(). Thanks.
