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i40e: use valid online CPU on q_vector initialization 

Currently, the q_vector initialization routine sets the affinity_mask
of a q_vector based on v_idx value. Meaning a loop iterates on v_idx,
which is an incremental value, and the cpumask is created based on
this value.

This is a problem in systems with multiple logical CPUs per core (like in
SMT scenarios). If we disable some logical CPUs, by turning SMT off for
example, we will end up with a sparse cpu_online_mask, i.e., only the first
CPU in a core is online, and incremental filling in q_vector cpumask might
lead to multiple offline CPUs being assigned to q_vectors.

Example: if we have a system with 8 cores each one containing 8 logical
CPUs (SMT == 8 in this case), we have 64 CPUs in total. But if SMT is
disabled, only the 1st CPU in each core remains online, so the
cpu_online_mask in this case would have only 8 bits set, in a sparse way.

In general case, when SMT is off the cpu_online_mask has only C bits set:
0, 1*N, 2*N, ..., C*(N-1)  where
C == # of cores;
N == # of logical CPUs per core.
In our example, only bits 0, 8, 16, 24, 32, 40, 48, 56 would be set.

This patch changes the way q_vector's affinity_mask is created: it iterates
on v_idx, but consumes the CPU index from the cpu_online_mask instead of
just using the v_idx incremental value.

No functional changes were introduced.

Signed-off-by: Guilherme G Piccoli <gpiccoli@linux.vnet.ibm.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Guilherme G. Piccoli 2016-06-27 12:16:43 -03:00 committed by Jeff Kirsher
parent 4b732cd4bb
commit 7f6c553902
1 changed files with 11 additions and 5 deletions
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16
drivers/net/ethernet/intel/i40e/i40e_main.c
View File

@ -7721,10 +7721,11 @@ static int i40e_init_msix(struct i40e_pf *pf)
* i40e_vsi_alloc_q_vector - Allocate memory for a single interrupt vector
* @vsi: the VSI being configured
* @v_idx: index of the vector in the vsi struct
* @cpu: cpu to be used on affinity_mask
*
* We allocate one q_vector. If allocation fails we return -ENOMEM.
**/
static int i40e_vsi_alloc_q_vector(struct i40e_vsi *vsi, int v_idx)
static int i40e_vsi_alloc_q_vector(struct i40e_vsi *vsi, int v_idx, int cpu)
{
struct i40e_q_vector *q_vector;
@ -7735,7 +7736,8 @@ static int i40e_vsi_alloc_q_vector(struct i40e_vsi *vsi, int v_idx)
q_vector->vsi = vsi;
q_vector->v_idx = v_idx;
cpumask_set_cpu(v_idx, &q_vector->affinity_mask);
cpumask_set_cpu(cpu, &q_vector->affinity_mask);
if (vsi->netdev)
netif_napi_add(vsi->netdev, &q_vector->napi,
i40e_napi_poll, NAPI_POLL_WEIGHT);
@ -7759,8 +7761,7 @@ static int i40e_vsi_alloc_q_vector(struct i40e_vsi *vsi, int v_idx)
static int i40e_vsi_alloc_q_vectors(struct i40e_vsi *vsi)
{
struct i40e_pf *pf = vsi->back;
int v_idx, num_q_vectors;
int err;
int err, v_idx, num_q_vectors, current_cpu;
/* if not MSIX, give the one vector only to the LAN VSI */
if (pf->flags & I40E_FLAG_MSIX_ENABLED)
@ -7770,10 +7771,15 @@ static int i40e_vsi_alloc_q_vectors(struct i40e_vsi *vsi)
else
return -EINVAL;
current_cpu = cpumask_first(cpu_online_mask);
for (v_idx = 0; v_idx < num_q_vectors; v_idx++) {
err = i40e_vsi_alloc_q_vector(vsi, v_idx);
err = i40e_vsi_alloc_q_vector(vsi, v_idx, current_cpu);
if (err)
goto err_out;
current_cpu = cpumask_next(current_cpu, cpu_online_mask);
if (unlikely(current_cpu >= nr_cpu_ids))
current_cpu = cpumask_first(cpu_online_mask);
}
return 0;