On Fri, Jul 28, 2017 at 12:30:54AM +0300, Michael S. Tsirkin wrote: > On Thu, Jul 27, 2017 at 04:14:30PM -0500, Seth Forshee wrote: > > On Thu, Jul 27, 2017 at 11:38:52PM +0300, Michael S. Tsirkin wrote: > > > On Thu, Jul 27, 2017 at 12:09:42PM -0500, Seth Forshee wrote: > > > > 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. > > > > > > So just wget that URL should be enough? > > > > Yes. Note that sometimes it starts out faster then slows down. > > > > 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 > > > > > > > > > Interesting. A more likely suspect would be > > > e377fcc8486d40867c6c217077ad0fa40977e060 - could you please try > > > reverting that one instead? > > > > I tried it, and I still get slow download speeds. I did test at > > 680557cf79f82623e2c4fd42733077d60a843513 during the bisect so I'm > > reasonably confident that this is the one where things went bad. > > > Also, could you please look at mergeable_rx_buffer_size in sysfs with > > > and without the change? > > > > In all cases (stock 4.13-rc2, 680557cf79f8 reverted, and e377fcc8486d > > reverted) mergeable_rx_buffer_size was 1536. > > > > Thanks, > > Seth > > Do you see any error counters incrementing after it slows down? I see rx_dropped and rx_length_errors increasing in lockstep once it slows down. Thanks, Seth _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
