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>

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index 9f1ac3a2591146aca77412d72638c7ba0dd4921e..487df9499c35d9ec2269c08a94a39461736de091 100644 (file)
--- 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);