Messages in this thread Patch in this message | | | From | Nitesh Narayan Lal <> | Subject | [Patch v1] i40e: limit the msix vectors based on housekeeping CPUs | Date | Mon, 15 Jun 2020 16:21:25 -0400 |
| |
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 online CPUs by using housekeeping_cpumask() to derive the number of available housekeeping CPUs.
Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com> --- drivers/net/ethernet/intel/i40e/i40e_main.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c index 5d807c8004f8..9691bececb86 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> /* Local includes */ #include "i40e.h" @@ -10933,11 +10934,13 @@ static int i40e_reserve_msix_vectors(struct i40e_pf *pf, int vectors) static int i40e_init_msix(struct i40e_pf *pf) { struct i40e_hw *hw = &pf->hw; + const struct cpumask *mask; int cpus, extra_vectors; int vectors_left; int v_budget, i; int v_actual; int iwarp_requested = 0; + int hk_flags; if (!(pf->flags & I40E_FLAG_MSIX_ENABLED)) return -ENODEV; @@ -10968,12 +10971,15 @@ static int i40e_init_msix(struct i40e_pf *pf) /* reserve some vectors for the main PF traffic queues. Initially we * only reserve at most 50% of the available vectors, in the case that - * the number of online CPUs is large. This ensures that we can enable - * extra features as well. Once we've enabled the other features, we - * will use any remaining vectors to reach as close as we can to the - * number of online CPUs. + * the number of online (housekeeping) CPUs is large. This ensures that + * we can enable extra features as well. Once we've enabled the other + * features, we will use any remaining vectors to reach as close as we + * can to the number of online (housekeeping) CPUs. */ - cpus = num_online_cpus(); + hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ; + mask = housekeeping_cpumask(hk_flags); + cpus = cpumask_weight(mask); + pf->num_lan_msix = min_t(int, cpus, vectors_left / 2); vectors_left -= pf->num_lan_msix; -- 2.18.4
| |