On Fri, 08 Mar, 2024 19:43:57 +0000 Haiyang Zhang <[email protected]> wrote: >> -----Original Message----- >> From: Jakub Kicinski <[email protected]> >> Sent: Friday, March 8, 2024 2:23 PM >> To: Haiyang Zhang <[email protected]> >> Cc: Shradha Gupta <[email protected]>; Shradha Gupta >> <[email protected]>; [email protected]; linux- >> [email protected]; [email protected]; >> [email protected]; Eric Dumazet <[email protected]>; Paolo Abeni >> <[email protected]>; Ajay Sharma <[email protected]>; Leon >> Romanovsky <[email protected]>; Thomas Gleixner <[email protected]>; >> Sebastian Andrzej Siewior <[email protected]>; KY Srinivasan >> <[email protected]>; Wei Liu <[email protected]>; Dexuan Cui >> <[email protected]>; Long Li <[email protected]>; Michael Kelley >> <[email protected]> >> Subject: Re: [PATCH] net :mana : Add per-cpu stats for MANA device >> >> On Fri, 8 Mar 2024 18:51:58 +0000 Haiyang Zhang wrote: >> > > Dynamic is a bit of an exaggeration, right? On a well-configured >> system >> > > each CPU should use a single queue assigned thru XPS. And for manual >> > > debug bpftrace should serve the purpose quite well. >> > >> > Some programs, like irqbalancer can dynamically change the CPU >> affinity, >> > so we want to add the per-CPU counters for better understanding of the >> CPU >> > usage. >> >> Do you have experimental data showing this making a difference >> in production? > Shradha, could you please add some data before / after enabling irqbalancer > which changes cpu affinity? > >> >> Seems unlikely, but if it does work we should enable it for all >> devices, no driver by driver. > There are some existing drivers, like mlx, rmnet, netvsc, etc. using percpu > counters. Are you suggesting we add a common API for all drivers?
Wanted to chime in with regards to mlx. You might be conflating per-cpu with per-queue. When we run ethtool -S, we present counters per netdev queue rather than per-cpu. The number of queues we instantiate is related to CPUs but it not always 1-1. Jakub just recently supported a proper interface for per-queue stats counters that we are interested in supporting. https://lore.kernel.org/netdev/[email protected]/ -- Thanks, Rahul Rameshbabu
