mmc: fix async request mechanism for sequential read scenarios
When current request is running on the bus and if next request fetched
by mmcqd is NULL, mmc context (mmcqd thread) gets blocked until the
current request completes. This means that if new request comes in while
the mmcqd thread is blocked, this new request can not be prepared in
parallel to current ongoing request. This may result in delaying the new
request execution and increase it's latency.
This change allows to wake up the MMC thread on new request arrival.
Now once the MMC thread is woken up, a new request can be fetched and
prepared in parallel to the current running request which means this new
request can be started immediately after the current running request
completes.
With this change read throughput is improved by 16%.
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Reviewed-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 21056b9..f79b4688 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -113,17 +113,6 @@
static DEFINE_MUTEX(open_lock);
-enum mmc_blk_status {
- MMC_BLK_SUCCESS = 0,
- MMC_BLK_PARTIAL,
- MMC_BLK_CMD_ERR,
- MMC_BLK_RETRY,
- MMC_BLK_ABORT,
- MMC_BLK_DATA_ERR,
- MMC_BLK_ECC_ERR,
- MMC_BLK_NOMEDIUM,
-};
-
module_param(perdev_minors, int, 0444);
MODULE_PARM_DESC(perdev_minors, "Minors numbers to allocate per device");
@@ -1364,8 +1353,11 @@
} else
areq = NULL;
areq = mmc_start_req(card->host, areq, (int *) &status);
- if (!areq)
+ if (!areq) {
+ if (status == MMC_BLK_NEW_REQUEST)
+ mq->flags |= MMC_QUEUE_NEW_REQUEST;
return 0;
+ }
mq_rq = container_of(areq, struct mmc_queue_req, mmc_active);
brq = &mq_rq->brq;
@@ -1438,6 +1430,10 @@
break;
case MMC_BLK_NOMEDIUM:
goto cmd_abort;
+ default:
+ pr_err("%s: Unhandled return value (%d)",
+ req->rq_disk->disk_name, status);
+ goto cmd_abort;
}
if (ret) {
@@ -1472,6 +1468,8 @@
int ret;
struct mmc_blk_data *md = mq->data;
struct mmc_card *card = md->queue.card;
+ struct mmc_host *host = card->host;
+ unsigned long flags;
if (req && !mq->mqrq_prev->req)
/* claim host only for the first request */
@@ -1486,6 +1484,7 @@
goto out;
}
+ mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
if (req && req->cmd_flags & REQ_DISCARD) {
/* complete ongoing async transfer before issuing discard */
if (card->host->areq)
@@ -1501,11 +1500,16 @@
mmc_blk_issue_rw_rq(mq, NULL);
ret = mmc_blk_issue_flush(mq, req);
} else {
+ if (!req && host->areq) {
+ spin_lock_irqsave(&host->context_info.lock, flags);
+ host->context_info.is_waiting_last_req = true;
+ spin_unlock_irqrestore(&host->context_info.lock, flags);
+ }
ret = mmc_blk_issue_rw_rq(mq, req);
}
out:
- if (!req)
+ if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST))
/* release host only when there are no more requests */
mmc_release_host(card->host);
return ret;