mmc: do not pack random requests
Packed commands causes higher latency since the completion of each
request is sent to the upper layer upon completion of the complete
packed request.
The benefit from this feature is card dependent. Some of the card
vendors do not have any benefit from using packed commands for random
requests. In case there is no benefit in random requests packing,
it is better to disable the packing to prevent this high latency.
This patch also add the new stop packing reason to the write packing
statistics.
Change-Id: I141887dcef2ceee14848634cc27c3c85f8edc7a5
Signed-off-by: Maya Erez <merez@codeaurora.org>
[merez@codeaurora.org: fix conflicts due to removal of BKOPS]
Signed-off-by: Maya Erez <merez@codeaurora.org>
[xiaonian@codeaurora.org: fix trivial merge conflict]
Signed-off-by: Xiaonian Wang <xiaonian@codeaurora.org>
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index d815bf6..7a1c615 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -128,6 +128,7 @@
struct device_attribute force_ro;
struct device_attribute power_ro_lock;
struct device_attribute num_wr_reqs_to_start_packing;
+ struct device_attribute no_pack_for_random;
int area_type;
};
@@ -295,6 +296,55 @@
}
static ssize_t
+no_pack_for_random_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int ret;
+
+ ret = snprintf(buf, PAGE_SIZE, "%d\n", md->queue.no_pack_for_random);
+
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t
+no_pack_for_random_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int value;
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ struct mmc_card *card = md->queue.card;
+ int ret = count;
+
+ if (!card) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ sscanf(buf, "%d", &value);
+
+ if (value < 0) {
+ pr_err("%s: value %d is not valid. old value remains = %d",
+ mmc_hostname(card->host), value,
+ md->queue.no_pack_for_random);
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ md->queue.no_pack_for_random = (value > 0) ? true : false;
+
+ pr_debug("%s: no_pack_for_random: new value = %d",
+ mmc_hostname(card->host),
+ md->queue.no_pack_for_random);
+
+exit:
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t
num_wr_reqs_to_start_packing_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -2170,6 +2220,15 @@
break;
}
+ if (mq->no_pack_for_random) {
+ if ((blk_rq_pos(cur) + blk_rq_sectors(cur)) !=
+ blk_rq_pos(next)) {
+ MMC_BLK_UPDATE_STOP_REASON(stats, RANDOM);
+ put_back = 1;
+ break;
+ }
+ }
+
if (rq_data_dir(next) == WRITE)
mq->num_of_potential_packed_wr_reqs++;
list_add_tail(&next->queuelist, &mqrq->packed->list);
@@ -2978,8 +3037,21 @@
if (ret)
goto num_wr_reqs_to_start_packing_fail;
+ md->no_pack_for_random.show = no_pack_for_random_show;
+ md->no_pack_for_random.store = no_pack_for_random_store;
+ sysfs_attr_init(&md->no_pack_for_random.attr);
+ md->no_pack_for_random.attr.name = "no_pack_for_random";
+ md->no_pack_for_random.attr.mode = S_IRUGO | S_IWUSR;
+ ret = device_create_file(disk_to_dev(md->disk),
+ &md->no_pack_for_random);
+ if (ret)
+ goto no_pack_for_random_fails;
+
return ret;
+no_pack_for_random_fails:
+ device_remove_file(disk_to_dev(md->disk),
+ &md->num_wr_reqs_to_start_packing);
num_wr_reqs_to_start_packing_fail:
device_remove_file(disk_to_dev(md->disk), &md->power_ro_lock);
power_ro_lock_fail: