@@ -22,3 +22,9 @@ switching-sched.txt
- Switching I/O schedulers at runtime
writeback_cache_control.txt
- Control of volatile write back caches
+mmc-max-speed.txt
+ - eMMC layer speed simulation, related to /sys/block/mmcblk*/
+ attributes:
+ max_read_speed
+ max_write_speed
+ cache_size
new file mode 100644
@@ -0,0 +1,38 @@
+eMMC Block layer simulation speed controls in /sys/block/mmcblk*/
+===============================================
+
+Turned on with CONFIG_MMC_SIMULATE_MAX_SPEED which enables MMC device speed
+limiting. Used to test and simulate the behavior of the system when
+confronted with a slow MMC.
+
+Enables max_read_speed, max_write_speed and cache_size attributes and module
+default parameters to control the write or read maximum KB/second speed
+behaviors.
+
+NB: There is room for improving the algorithm for aspects tied directly to
+eMMC specific behavior. For instance, wear leveling and stalls from an
+exhausted erase pool. We would expect that if there was a need to provide
+similar speed simulation controls to other types of block devices, aspects of
+their behavior are modelled separately (e.g. head seek times, heat assist,
+shingling and rotational latency).
+
+/sys/block/mmcblk0/max_read_speed:
+
+Number of KB/second reads allowed to the block device. Used to test and
+simulate the behavior of the system when confronted with a slow reading MMC.
+Set to 0 or "off" to place no speed limit.
+
+/sys/block/mmcblk0/max_write_speed:
+
+Number of KB/second writes allowed to the block device. Used to test and
+simulate the behavior of the system when confronted with a slow writing MMC.
+Set to 0 or "off" to place no speed limit.
+
+/sys/block/mmcblk0/cache_size:
+
+Number of MB of high speed memory or high speed SLC cache expected on the
+eMMC device being simulated. Used to help simulate the write-back behavior
+more accurately. The assumption is the cache has no delay, but draws down
+in the background to the MLC/TLC primary store at the max_write_speed rate.
+Any write speed delays will show up when the cache is full, or when an I/O
+request to flush is issued.
@@ -77,3 +77,15 @@ config MMC_TEST
This driver is only of interest to those developing or
testing a host driver. Most people should say N here.
+
+config MMC_SIMULATE_MAX_SPEED
+ bool "Turn on maximum speed control per block device"
+ depends on MMC_BLOCK
+ help
+ Say Y here to enable MMC device speed limiting. Used to test and
+ simulate the behavior of the system when confronted with a slow MMC.
+
+ Enables max_read_speed, max_write_speed and cache_size attributes to
+ control the write or read maximum KB/second speed behaviors.
+
+ If unsure, say N here.
@@ -284,6 +284,250 @@ out:
return ret;
}
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+
+static int max_read_speed, max_write_speed, cache_size = 4;
+
+module_param(max_read_speed, int, S_IRUSR | S_IRGRP);
+MODULE_PARM_DESC(max_read_speed, "maximum KB/s read speed 0=off");
+module_param(max_write_speed, int, S_IRUSR | S_IRGRP);
+MODULE_PARM_DESC(max_write_speed, "maximum KB/s write speed 0=off");
+module_param(cache_size, int, S_IRUSR | S_IRGRP);
+MODULE_PARM_DESC(cache_size, "MB high speed memory or SLC cache");
+
+/*
+ * helper macros and expectations:
+ * size - unsigned long number of bytes
+ * jiffies - unsigned long HZ timestamp difference
+ * speed - unsigned KB/s transfer rate
+ */
+#define size_and_speed_to_jiffies(size, speed) \
+ ((size) * HZ / (speed) / 1024UL)
+#define jiffies_and_speed_to_size(jiffies, speed) \
+ (((speed) * (jiffies) * 1024UL) / HZ)
+#define jiffies_and_size_to_speed(jiffies, size) \
+ ((size) * HZ / (jiffies) / 1024UL)
+
+/* Limits to report warning */
+/* jiffies_and_size_to_speed(10*HZ, queue_max_hw_sectors(q) * 512UL) ~ 25 */
+#define MIN_SPEED(q) 250 /* 10 times faster than a floppy disk */
+#define MAX_SPEED(q) jiffies_and_size_to_speed(1, queue_max_sectors(q) * 512UL)
+
+#define speed_valid(speed) ((speed) > 0)
+
+static const char off[] = "off\n";
+
+static int max_speed_show(int speed, char *buf)
+{
+ if (speed)
+ return scnprintf(buf, PAGE_SIZE, "%uKB/s\n", speed);
+ else
+ return scnprintf(buf, PAGE_SIZE, off);
+}
+
+static int max_speed_store(const char *buf, struct request_queue *q)
+{
+ unsigned int limit, set = 0;
+
+ if (!strncasecmp(off, buf, sizeof(off) - 2))
+ return set;
+ if (kstrtouint(buf, 0, &set) || (set > INT_MAX))
+ return -EINVAL;
+ if (set == 0)
+ return set;
+ limit = MAX_SPEED(q);
+ if (set > limit)
+ pr_warn("max speed %u ineffective above %u\n", set, limit);
+ limit = MIN_SPEED(q);
+ if (set < limit)
+ pr_warn("max speed %u painful below %u\n", set, limit);
+ return set;
+}
+
+static ssize_t max_write_speed_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int ret = max_speed_show(atomic_read(&md->queue.max_write_speed), buf);
+
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t max_write_speed_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int set = max_speed_store(buf, md->queue.queue);
+
+ if (set < 0) {
+ mmc_blk_put(md);
+ return set;
+ }
+
+ atomic_set(&md->queue.max_write_speed, set);
+ mmc_blk_put(md);
+ return count;
+}
+
+static const DEVICE_ATTR(max_write_speed, S_IRUGO | S_IWUSR,
+ max_write_speed_show, max_write_speed_store);
+
+static ssize_t max_read_speed_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int ret = max_speed_show(atomic_read(&md->queue.max_read_speed), buf);
+
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t max_read_speed_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int set = max_speed_store(buf, md->queue.queue);
+
+ if (set < 0) {
+ mmc_blk_put(md);
+ return set;
+ }
+
+ atomic_set(&md->queue.max_read_speed, set);
+ mmc_blk_put(md);
+ return count;
+}
+
+static const DEVICE_ATTR(max_read_speed, S_IRUGO | S_IWUSR,
+ max_read_speed_show, max_read_speed_store);
+
+static ssize_t cache_size_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ struct mmc_queue *mq = &md->queue;
+ int cache_size = atomic_read(&mq->cache_size);
+ int ret;
+
+ if (!cache_size)
+ ret = scnprintf(buf, PAGE_SIZE, off);
+ else {
+ int speed = atomic_read(&mq->max_write_speed);
+
+ if (!speed_valid(speed))
+ ret = scnprintf(buf, PAGE_SIZE, "%uMB\n", cache_size);
+ else { /* We accept race between cache_jiffies and cache_used */
+ unsigned long size = jiffies_and_speed_to_size(
+ jiffies - mq->cache_jiffies, speed);
+ long used = atomic_long_read(&mq->cache_used);
+
+ if (size >= used)
+ size = 0;
+ else
+ size = (used - size) * 100 / cache_size
+ / 1024UL / 1024UL;
+
+ ret = scnprintf(buf, PAGE_SIZE, "%uMB %lu%% used\n",
+ cache_size, size);
+ }
+ }
+
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t cache_size_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct mmc_blk_data *md;
+ unsigned int set = 0;
+
+ if (strncasecmp(off, buf, sizeof(off) - 2)
+ && (kstrtouint(buf, 0, &set) || (set > INT_MAX)))
+ return -EINVAL;
+
+ md = mmc_blk_get(dev_to_disk(dev));
+ atomic_set(&md->queue.cache_size, set);
+ mmc_blk_put(md);
+ return count;
+}
+
+static const DEVICE_ATTR(cache_size, S_IRUGO | S_IWUSR,
+ cache_size_show, cache_size_store);
+
+/* correct for write-back */
+static long mmc_blk_cache_used(struct mmc_queue *mq, unsigned long waitfor)
+{
+ long used = 0;
+ int speed = atomic_read(&mq->max_write_speed);
+
+ if (speed_valid(speed)) {
+ unsigned long size = jiffies_and_speed_to_size(
+ waitfor - mq->cache_jiffies, speed);
+ used = atomic_long_read(&mq->cache_used);
+
+ if (size >= used)
+ used = 0;
+ else
+ used -= size;
+ }
+
+ atomic_long_set(&mq->cache_used, used);
+ mq->cache_jiffies = waitfor;
+
+ return used;
+}
+
+static void mmc_blk_simulate_delay(
+ struct mmc_queue *mq,
+ struct request *req,
+ unsigned long waitfor)
+{
+ int max_speed;
+
+ if (!req)
+ return;
+
+ max_speed = (rq_data_dir(req) == READ)
+ ? atomic_read(&mq->max_read_speed)
+ : atomic_read(&mq->max_write_speed);
+ if (speed_valid(max_speed)) {
+ unsigned long bytes = blk_rq_bytes(req);
+
+ if (rq_data_dir(req) != READ) {
+ int cache_size = atomic_read(&mq->cache_size);
+
+ if (cache_size) {
+ unsigned long size = cache_size * 1024L * 1024L;
+ long used = mmc_blk_cache_used(mq, waitfor);
+
+ used += bytes;
+ atomic_long_set(&mq->cache_used, used);
+ bytes = 0;
+ if (used > size)
+ bytes = used - size;
+ }
+ }
+ waitfor += size_and_speed_to_jiffies(bytes, max_speed);
+ if (time_is_after_jiffies(waitfor)) {
+ long msecs = jiffies_to_msecs(waitfor - jiffies);
+
+ if (likely(msecs > 0))
+ msleep(msecs);
+ }
+ }
+}
+
+#else
+
+#define mmc_blk_simulate_delay(mq, req, waitfor)
+
+#endif
+
static int mmc_blk_open(struct block_device *bdev, fmode_t mode)
{
struct mmc_blk_data *md = mmc_blk_get(bdev->bd_disk);
@@ -1207,6 +1451,23 @@ static int mmc_blk_issue_flush(struct mmc_queue *mq, struct request *req)
if (ret)
ret = -EIO;
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ else if (atomic_read(&mq->cache_size)) {
+ long used = mmc_blk_cache_used(mq, jiffies);
+
+ if (used) {
+ int speed = atomic_read(&mq->max_write_speed);
+
+ if (speed_valid(speed)) {
+ unsigned long msecs = jiffies_to_msecs(
+ size_and_speed_to_jiffies(
+ used, speed));
+ if (msecs)
+ msleep(msecs);
+ }
+ }
+ }
+#endif
blk_end_request_all(req, ret);
return ret ? 0 : 1;
@@ -1908,6 +2169,9 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
struct mmc_async_req *areq;
const u8 packed_nr = 2;
u8 reqs = 0;
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ unsigned long waitfor = jiffies;
+#endif
if (!rqc && !mq->mqrq_prev->req)
return 0;
@@ -1958,6 +2222,8 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
*/
mmc_blk_reset_success(md, type);
+ mmc_blk_simulate_delay(mq, rqc, waitfor);
+
if (mmc_packed_cmd(mq_rq->cmd_type)) {
ret = mmc_blk_end_packed_req(mq_rq);
break;
@@ -2381,6 +2647,14 @@ static void mmc_blk_remove_req(struct mmc_blk_data *md)
card->ext_csd.boot_ro_lockable)
device_remove_file(disk_to_dev(md->disk),
&md->power_ro_lock);
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ device_remove_file(disk_to_dev(md->disk),
+ &dev_attr_max_write_speed);
+ device_remove_file(disk_to_dev(md->disk),
+ &dev_attr_max_read_speed);
+ device_remove_file(disk_to_dev(md->disk),
+ &dev_attr_cache_size);
+#endif
/* Stop new requests from getting into the queue */
del_gendisk(md->disk);
@@ -2422,6 +2696,24 @@ static int mmc_add_disk(struct mmc_blk_data *md)
ret = device_create_file(disk_to_dev(md->disk), &md->force_ro);
if (ret)
goto force_ro_fail;
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ atomic_set(&md->queue.max_write_speed, max_write_speed);
+ ret = device_create_file(disk_to_dev(md->disk),
+ &dev_attr_max_write_speed);
+ if (ret)
+ goto max_write_speed_fail;
+ atomic_set(&md->queue.max_read_speed, max_read_speed);
+ ret = device_create_file(disk_to_dev(md->disk),
+ &dev_attr_max_read_speed);
+ if (ret)
+ goto max_read_speed_fail;
+ atomic_set(&md->queue.cache_size, cache_size);
+ atomic_long_set(&md->queue.cache_used, 0);
+ md->queue.cache_jiffies = jiffies;
+ ret = device_create_file(disk_to_dev(md->disk), &dev_attr_cache_size);
+ if (ret)
+ goto cache_size_fail;
+#endif
if ((md->area_type & MMC_BLK_DATA_AREA_BOOT) &&
card->ext_csd.boot_ro_lockable) {
@@ -2446,6 +2738,14 @@ static int mmc_add_disk(struct mmc_blk_data *md)
return ret;
power_ro_lock_fail:
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ device_remove_file(disk_to_dev(md->disk), &dev_attr_cache_size);
+cache_size_fail:
+ device_remove_file(disk_to_dev(md->disk), &dev_attr_max_read_speed);
+max_read_speed_fail:
+ device_remove_file(disk_to_dev(md->disk), &dev_attr_max_write_speed);
+max_write_speed_fail:
+#endif
device_remove_file(disk_to_dev(md->disk), &md->force_ro);
force_ro_fail:
del_gendisk(md->disk);
@@ -57,6 +57,14 @@ struct mmc_queue {
struct mmc_queue_req mqrq[2];
struct mmc_queue_req *mqrq_cur;
struct mmc_queue_req *mqrq_prev;
+#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
+ atomic_t max_write_speed;
+ atomic_t max_read_speed;
+ atomic_t cache_size;
+ /* i/o tracking */
+ atomic_long_t cache_used;
+ unsigned long cache_jiffies;
+#endif
};
extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, spinlock_t *,
When CONFIG_MMC_SIMULATE_MAX_SPEED is enabled, Expose max_read_speed, max_write_speed and cache_size default module parameters and sysfs controls to simulate a slow eMMC device. Default values are 0 (off), 0 (off) and 4 MB respectively. Signed-off-by: Mark Salyzyn <salyzyn@android.com> --- changes in v2: change from CONFIG_MMC_BLOCK_MAX_SPEED to CONFIG_MMC_SIMULATE_MAX_SPEED. Add documentation. changes in v3: switch to using module parameters. Documentation/block/00-INDEX | 6 + Documentation/block/mmc-max-speed.txt | 38 +++++ drivers/mmc/card/Kconfig | 12 ++ drivers/mmc/card/block.c | 300 ++++++++++++++++++++++++++++++++++ drivers/mmc/card/queue.h | 8 + 5 files changed, 364 insertions(+) create mode 100644 Documentation/block/mmc-max-speed.txt