sfc: Move CPU counting for RSS into a separate function, efx_wanted_rx_queues()

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 35 insertions, 25 deletions

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 9f1ac3a25911..487df9499c35 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -819,38 +819,48 @@ static void efx_fini_io(struct efx_nic *efx)
         pci_disable_device(efx->pci_dev);
 }
 
-/* Probe the number and type of interrupts we are able to obtain. */
+/* Get number of RX queues wanted.  Return number of online CPU
+ * packages in the expectation that an IRQ balancer will spread
+ * interrupts across them. */
+static int efx_wanted_rx_queues(void)
+{
+        cpumask_t core_mask;
+        int count;
+        int cpu;
+
+        cpus_clear(core_mask);
+        count = 0;
+        for_each_online_cpu(cpu) {
+                if (!cpu_isset(cpu, core_mask)) {
+                        ++count;
+                        cpus_or(core_mask, core_mask,
+                                topology_core_siblings(cpu));
+                }
+        }
+
+        return count;
+}
+
+/* Probe the number and type of interrupts we are able to obtain, and
+ * the resulting numbers of channels and RX queues.
+ */
 static void efx_probe_interrupts(struct efx_nic *efx)
 {
-        int max_channel = efx->type->phys_addr_channels - 1;
-        struct msix_entry xentries[EFX_MAX_CHANNELS];
+        int max_channels =
+                min_t(int, efx->type->phys_addr_channels, EFX_MAX_CHANNELS);
         int rc, i;
 
         if (efx->interrupt_mode == EFX_INT_MODE_MSIX) {
-                BUG_ON(!pci_find_capability(efx->pci_dev, PCI_CAP_ID_MSIX));
-
-                if (rss_cpus == 0) {
-                        cpumask_t core_mask;
-                        int cpu;
-
-                        cpus_clear(core_mask);
-                        efx->rss_queues = 0;
-                        for_each_online_cpu(cpu) {
-                                if (!cpu_isset(cpu, core_mask)) {
-                                        ++efx->rss_queues;
-                                        cpus_or(core_mask, core_mask,
-                                                topology_core_siblings(cpu));
-                                }
-                        }
-                } else {
-                        efx->rss_queues = rss_cpus;
-                }
+                struct msix_entry xentries[EFX_MAX_CHANNELS];
+                int wanted_ints;
 
-                efx->rss_queues = min(efx->rss_queues, max_channel + 1);
-                efx->rss_queues = min(efx->rss_queues, EFX_MAX_CHANNELS);
+                /* We want one RX queue and interrupt per CPU package
+                 * (or as specified by the rss_cpus module parameter).
+                 * We will need one channel per interrupt.
+                 */
+                wanted_ints = rss_cpus ? rss_cpus : efx_wanted_rx_queues();
+                efx->rss_queues = min(wanted_ints, max_channels);
 
-                /* Request maximum number of MSI interrupts, and fill out
-                 * the channel interrupt information the allowed allocation */
                 for (i = 0; i < efx->rss_queues; i++)
                         xentries[i].entry = i;
                 rc = pci_enable_msix(efx->pci_dev, xentries, efx->rss_queues);