On Wed, 8 Apr 2015 21:46:19 +0000 (UTC) Jim Harris <jimhar...@freebsd.org> wrote:
> Author: jimharris > Date: Wed Apr 8 21:46:18 2015 > New Revision: 281280 > URL: https://svnweb.freebsd.org/changeset/base/281280 > > Log: > nvme: fall back to a smaller MSI-X vector allocation if necessary > > Previously, if per-CPU MSI-X vectors could not be allocated, > nvme(4) would fall back to INTx with a single I/O queue pair. > This change will still fall back to a single I/O queue pair, but > allocate MSI-X vectors instead of reverting to INTx. > > MFC after: 1 week > Sponsored by: Intel > > Modified: > head/sys/dev/nvme/nvme_ctrlr.c > > Modified: head/sys/dev/nvme/nvme_ctrlr.c > ============================================================================== > --- head/sys/dev/nvme/nvme_ctrlr.c Wed Apr 8 21:10:13 > 2015 (r281279) +++ head/sys/dev/nvme/nvme_ctrlr.c Wed > Apr 8 21:46:18 2015 (r281280) @@ -1144,9 +1144,17 @@ > nvme_ctrlr_construct(struct nvme_control /* One vector per IO queue, > plus one vector for admin queue. */ num_vectors = > ctrlr->num_io_queues + 1; > - if (pci_msix_count(dev) < num_vectors) { > + /* > + * If we cannot even allocate 2 vectors (one for admin, one > for > + * I/O), then revert to INTx. > + */ > + if (pci_msix_count(dev) < 2) { > ctrlr->msix_enabled = 0; > goto intx; > + } else if (pci_msix_count(dev) < num_vectors) { > + ctrlr->per_cpu_io_queues = FALSE; > + ctrlr->num_io_queues = 1; > + num_vectors = 2; /* one for admin, one for I/O */ > } > > if (pci_alloc_msix(dev, &num_vectors) != 0) { Huh, Linux just falls back to as many vectors as it can and just allocates them between per-cpu queues in a round-robin manner. I think is is a better approach than what we have here, would you consider it? -- Alexander Kabaev
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