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). > @Bobby Are these numbers for guest -> host communication? Can we try the > reverse path as well? > Yep, these are guest -> host. Unfortunately, the numbers are worse for host to guest. Running the same tests, except for 100+ times instead of just 10, for h2g sockets: 16B payload throughput decreases ~8%. 4K-8KB payload throughput decreases ~15%. 64KB payload throughput decreases ~8%. I'm currently working on tracking down the root cause and seeing if there is some way around the performance hit. Sorry for the delayed response, it took a good minute to collect enough data to feel confident I wasn't just seeing noise. Best, Bobby
