> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-boun...@osuosl.org> On Behalf Of
> Michal Schmidt
> Sent: Thursday, May 23, 2024 4:43 AM
> To: Brandeburg, Jesse <jesse.brandeb...@intel.com>; Nguyen, Anthony L
> <anthony.l.ngu...@intel.com>; intel-wired-...@lists.osuosl.org
> Cc: net...@vger.kernel.org; Thomas Gleixner <t...@linutronix.de>; Nitesh
> Narayan Lal <nit...@redhat.com>
> Subject: [Intel-wired-lan] [PATCH iwl-next] ice: use
> irq_update_affinity_hint()
>
> irq_set_affinity_hint() is deprecated. Use irq_update_affinity_hint()
> instead. This removes the side-effect of actually applying the affinity.
>
> The driver does not really need to worry about spreading its IRQs across
> CPUs. The core code already takes care of that.
> On the contrary, when the driver applies affinities by itself, it breaks the
> users' expectations:
> 1. The user configures irqbalance with IRQBALANCE_BANNED_CPULIST in
> order to prevent IRQs from being moved to certain CPUs that run a
> real-time workload.
> 2. ice reconfigures VSIs at runtime due to a MIB change
> (ice_dcb_process_lldp_set_mib_change). Reopening a VSI resets the
> affinity in ice_vsi_req_irq_msix().
> 3. ice has no idea about irqbalance's config, so it may move an IRQ to
> a banned CPU. The real-time workload suffers unacceptable latency.
>
> I am not sure if updating the affinity hints is at all useful, because
> irqbalance ignores them since 2016 ([1]), but at least it's harmless.
>
> This ice change is similar to i40e commit d34c54d1739c ("i40e: Use
> irq_update_affinity_hint()").
>
> [1] https://github.com/Irqbalance/irqbalance/commit/dcc411e7bfdd
>
> Signed-off-by: Michal Schmidt <mschm...@redhat.com>
> ---
> drivers/net/ethernet/intel/ice/ice_lib.c | 4 ++--
> drivers/net/ethernet/intel/ice/ice_main.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pu...@intel.com> (A
Contingent worker at Intel)
