I'm seeing a performance regression with virtio_net that looks to have started in 4.12-rc1. I only see it in one context though, downloading snap packages from the Ubuntu snap store. For example:
https://api.snapcraft.io/api/v1/snaps/download/b8X2psL1ryVrPt5WEmpYiqfr5emixTd7_1797.snap which redirects to Internap's CDN. Normally this downloads in a few seconds at ~10 MB/s, but with 4.12 and 4.13 it takes minutes with a rate of ~150 KB/s. Everything else I've tried downloads as normal speeds. I bisected this to 680557cf79f8 "virtio_net: rework mergeable buffer handling". If I revert this on top of 4.13-rc2 (along with other changes needed to successfully revert it) speeds return to normal. Thanks, Seth
