Wed, May 15, 2024 at 12:12:51PM CEST, jiri@xxxxxxxxxxx wrote: >Wed, May 15, 2024 at 10:20:04AM CEST, mst@xxxxxxxxxx wrote: >>On Wed, May 15, 2024 at 09:34:08AM +0200, Jiri Pirko wrote: >>> Fri, May 10, 2024 at 01:27:08PM CEST, mst@xxxxxxxxxx wrote: >>> >On Fri, May 10, 2024 at 01:11:49PM +0200, Jiri Pirko wrote: >>> >> Fri, May 10, 2024 at 12:52:52PM CEST, mst@xxxxxxxxxx wrote: >>> >> >On Fri, May 10, 2024 at 12:37:15PM +0200, Jiri Pirko wrote: >>> >> >> Thu, May 09, 2024 at 04:28:12PM CEST, mst@xxxxxxxxxx wrote: >>> >> >> >On Thu, May 09, 2024 at 03:31:56PM +0200, Jiri Pirko wrote: >>> >> >> >> Thu, May 09, 2024 at 02:41:39PM CEST, mst@xxxxxxxxxx wrote: >>> >> >> >> >On Thu, May 09, 2024 at 01:46:15PM +0200, Jiri Pirko wrote: >>> >> >> >> >> From: Jiri Pirko <jiri@xxxxxxxxxx> >>> >> >> >> >> >>> >> >> >> >> Add support for Byte Queue Limits (BQL). >>> >> >> >> >> >>> >> >> >> >> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx> >>> >> >> >> > >>> >> >> >> >Can we get more detail on the benefits you observe etc? >>> >> >> >> >Thanks! >>> >> >> >> >>> >> >> >> More info about the BQL in general is here: >>> >> >> >> https://lwn.net/Articles/469652/ >>> >> >> > >>> >> >> >I know about BQL in general. We discussed BQL for virtio in the past >>> >> >> >mostly I got the feedback from net core maintainers that it likely won't >>> >> >> >benefit virtio. >>> >> >> >>> >> >> Do you have some link to that, or is it this thread: >>> >> >> https://lore.kernel.org/netdev/21384cb5-99a6-7431-1039-b356521e1bc3@xxxxxxxxxx/ >>> >> > >>> >> > >>> >> >A quick search on lore turned up this, for example: >>> >> >https://lore.kernel.org/all/a11eee78-b2a1-3dbc-4821-b5f4bfaae819@xxxxxxxxx/ >>> >> >>> >> Says: >>> >> "Note that NIC with many TX queues make BQL almost useless, only adding extra >>> >> overhead." >>> >> >>> >> But virtio can have one tx queue, I guess that could be quite common >>> >> configuration in lot of deployments. >>> > >>> >Not sure we should worry about performance for these though. >>> >What I am saying is this should come with some benchmarking >>> >results. >>> >>> I did some measurements with VDPA, backed by ConnectX6dx NIC, single >>> queue pair: >>> >>> super_netperf 200 -H $ip -l 45 -t TCP_STREAM & >>> nice -n 20 netperf -H $ip -l 10 -t TCP_RR >>> >>> RR result with no bql: >>> 29.95 >>> 32.74 >>> 28.77 >>> >>> RR result with bql: >>> 222.98 >>> 159.81 >>> 197.88 >>> >> >>Okay. And on the other hand, any measureable degradation with >>multiqueue and when testing throughput? > >With multiqueue it depends if the flows hits the same queue or not. If >they do, the same results will likely be shown. RR 1q, w/o bql: 29.95 32.74 28.77 RR 1q, with bql: 222.98 159.81 197.88 RR 4q, w/o bql: 355.82 364.58 233.47 RR 4q, with bql: 371.19 255.93 337.77 So answer to your question is: "no measurable degradation with 4 queues". > > >> >> >>> >>> > >>> > >>> >> >>> >> > >>> >> > >>> >> > >>> >> > >>> >> >> I don't see why virtio should be any different from other >>> >> >> drivers/devices that benefit from bql. HOL blocking is the same here are >>> >> >> everywhere. >>> >> >> >>> >> >> > >>> >> >> >So I'm asking, what kind of benefit do you observe? >>> >> >> >>> >> >> I don't have measurements at hand, will attach them to v2. >>> >> >> >>> >> >> Thanks! >>> >> >> >>> >> >> > >>> >> >> >-- >>> >> >> >MST >>> >> >> > >>> >> > >>> > >>
