Allow multiple TRIMs to be done for nda

Don't call cam_iosched_trim_done or cam_iosched_submit_trim for nda
since its hardware can handle almost an arbitrary number of TRIMs and
we don't have to be careful to only ever do one.

Sponsored by: Netflix

1 files changed, 11 insertions, 2 deletions

diff --git a/sys/cam/nvme/nvme_da.c b/sys/cam/nvme/nvme_da.c
index 3e829a4e8e9b..8e4de784c3a1 100644
--- a/sys/cam/nvme/nvme_da.c
+++ b/sys/cam/nvme/nvme_da.c
@@ -920,7 +920,12 @@ ndastart(struct cam_periph *periph, union ccb *start_ccb)
 			nda_nvme_trim(softc, &start_ccb->nvmeio, dsm_range, 1);
 			start_ccb->ccb_h.ccb_state = NDA_CCB_TRIM;
 			start_ccb->ccb_h.flags |= CAM_UNLOCKED;
-			cam_iosched_submit_trim(softc->cam_iosched);	/* XXX */
+			/*
+			 * Note: We can have multiple TRIMs in flight, so we don't call
+			 * cam_iosched_submit_trim(softc->cam_iosched);
+			 * since that forces the I/O scheduler to only schedule one at a time.
+			 * On NVMe drives, this is a performance disaster.
+			 */
 			goto out;
 		}
 		case BIO_FLUSH:
@@ -1013,7 +1018,11 @@ ndadone(struct cam_periph *periph, union ccb *done_ccb)
 			TAILQ_INIT(&queue);
 			TAILQ_CONCAT(&queue, &softc->trim_req.bps, bio_queue);
 #endif
-			cam_iosched_trim_done(softc->cam_iosched);
+			/*
+			 * Since we can have multiple trims in flight, we don't
+			 * need to call this here.
+			 * cam_iosched_trim_done(softc->cam_iosched);
+			 */
 			ndaschedule(periph);
 			cam_periph_unlock(periph);
 #ifdef notyet