On Sat, Feb 3, 2024 at 12:01 AM Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > On Fri, 2 Feb 2024 14:52:59 +0800 Jason Xing wrote: > > > Can you say more? I'm curious what's your use case. > > > > I'm not working at Nvidia, so my point of view may differ from theirs. > > From what I can tell is that those two counters help me narrow down > > the range if I have to diagnose/debug some issues. > > right, i'm asking to collect useful debugging tricks, nothing against > the patch itself :) > > > 1) I sometimes notice that if some irq is held too long (say, one > > simple case: output of printk printed to the console), those two > > counters can reflect the issue. > > 2) Similarly in virtio net, recently I traced such counters the > > current kernel does not have and it turned out that one of the output > > queues in the backend behaves badly. > > ... > > > > Stop/wake queue counters may not show directly the root cause of the > > issue, but help us 'guess' to some extent. > > I'm surprised you say you can detect stall-related issues with this. > I guess virtio doesn't have BQL support, which makes it special. Yes, virtio-net has a legacy orphan mode, this is something that needs to be dropped in the future. This would make BQL much more easier to be implemented. > Normal HW drivers with BQL almost never stop the queue by themselves. > I mean - if they do, and BQL is active, then the system is probably > misconfigured (queue is too short). This is what we use at Meta to > detect stalls in drivers with BQL: > > https://lore.kernel.org/all/20240131102150.728960-3-leitao@xxxxxxxxxx/ > > Daniel, I think this may be a good enough excuse to add per-queue stats > to the netdev genl family, if you're up for that. LMK if you want more > info, otherwise I guess ethtool -S is fine for now. > Thanks
