On Wed, Sep 09, 2020 at 11:08:17AM -0400, Nitesh Narayan Lal wrote: > In a realtime environment, it is essential to isolate unwanted IRQs from > isolated CPUs to prevent latency overheads. Creating MSIX vectors only > based on the online CPUs could lead to a potential issue on an RT setup > that has several isolated CPUs but a very few housekeeping CPUs. This is > because in these kinds of setups an attempt to move the IRQs to the > limited housekeeping CPUs from isolated CPUs might fail due to the per > CPU vector limit. This could eventually result in latency spikes because > of the IRQ threads that we fail to move from isolated CPUs. > > This patch prevents i40e to add vectors only based on available > housekeeping CPUs by using num_housekeeping_cpus(). > > Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx> > --- > drivers/net/ethernet/intel/i40e/i40e_main.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c > index 2e433fdbf2c3..3b4cd4b3de85 100644 > --- a/drivers/net/ethernet/intel/i40e/i40e_main.c > +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c > @@ -5,6 +5,7 @@ > #include <linux/of_net.h> > #include <linux/pci.h> > #include <linux/bpf.h> > +#include <linux/sched/isolation.h> > #include <generated/utsrelease.h> > > /* Local includes */ > @@ -11002,7 +11003,7 @@ static int i40e_init_msix(struct i40e_pf *pf) > * will use any remaining vectors to reach as close as we can to the > * number of online CPUs. > */ > - cpus = num_online_cpus(); > + cpus = num_housekeeping_cpus(); > pf->num_lan_msix = min_t(int, cpus, vectors_left / 2); > vectors_left -= pf->num_lan_msix; > > -- > 2.27.0 For patches 1 and 2: Reviewed-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
