Commit 3870092d authored Sep 18, 2020 by Ben Walker Committed by Tomasz Zawadzki Sep 22, 2020

bdev/nvme: For reads, if there is only one element in the iov don't use


readv API

It's cheaper to call spdk_nvme_ns_cmd_read_with_md than it is to call
spdk_nvme_ns_cmd_readv_with_md, so do a quick check of the iovcnt and
use the best one for the job.

This is about a 15% improvement in I/Ops.

Change-Id: I82e6677d1ac47abf9919f95e651e7a7595c5e9a3
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/4316


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

parent 85ddcf6f

module/bdev/nvme/bdev_nvme.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -2595,10 +2595,18 @@ bdev_nvme_readv(struct nvme_bdev nbdev, struct spdk_io_channel ch,
		bio->iovpos = 0;
		bio->iov_offset = 0;

		if (iovcnt == 1) {
		rc = spdk_nvme_ns_cmd_read_with_md(nbdev->nvme_ns->ns, nvme_ch->qpair, iov[0].iov_base, md, lba,
		lba_count,
		bdev_nvme_readv_done, bio,
		nbdev->disk.dif_check_flags,
		0, 0);
		} else {
		rc = spdk_nvme_ns_cmd_readv_with_md(nbdev->nvme_ns->ns, nvme_ch->qpair, lba, lba_count,
		bdev_nvme_readv_done, bio, nbdev->disk.dif_check_flags,
		bdev_nvme_queued_reset_sgl, bdev_nvme_queued_next_sge,
		md, 0, 0);
		}

		if (rc != 0 && rc != -ENOMEM) {
		SPDK_ERRLOG("readv failed: rc = %d\n", rc);