[Intel-wired-lan] [PATCH v4 3/4] i40e: Limit msix vectors to housekeeping CPUs

Nitesh Narayan Lal nitesh at redhat.com
Mon Sep 28 18:35:28 UTC 2020


If we have isolated CPUs designated to perform real-time tasks, to keep the
latency overhead to a minimum for real-time CPUs IRQ vectors are moved to
housekeeping CPUs from the userspace. Creating MSIX vectors only based on
the online CPUs could lead to exhaustion of housekeeping CPU IRQ vectors in
such environments.

This patch prevents i40e to create vectors only based on online CPUs by
retrieving the online housekeeping CPUs that are designated to perform
managed IRQ jobs.

Signed-off-by: Nitesh Narayan Lal <nitesh at redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti at redhat.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg at intel.com>
---
 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..370b581cd48c 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 = housekeeping_num_online_cpus(HK_FLAG_MANAGED_IRQ);
 	pf->num_lan_msix = min_t(int, cpus, vectors_left / 2);
 	vectors_left -= pf->num_lan_msix;
 
-- 
2.18.2



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