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

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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>
This commit is contained in:
Ben Walker 2020-09-18 10:31:23 -07:00 committed by Tomasz Zawadzki
parent 85ddcf6f8d
commit 3870092dd1
1 changed files with 12 additions and 4 deletions
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16
module/bdev/nvme/bdev_nvme.c
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@ -2595,10 +2595,18 @@ bdev_nvme_readv(struct nvme_bdev *nbdev, struct spdk_io_channel *ch,
bio->iovpos = 0;
bio->iov_offset = 0;
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 (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);