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 <saly...@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 diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX index d18ecd8..52bda21 100644 --- a/Documentation/block/00-INDEX +++ b/Documentation/block/00-INDEX @@ -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 diff --git a/Documentation/block/mmc-max-speed.txt b/Documentation/block/mmc-max-speed.txt new file mode 100644 index 0000000..7b57f21 --- /dev/null +++ b/Documentation/block/mmc-max-speed.txt @@ -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. diff --git a/drivers/mmc/card/Kconfig b/drivers/mmc/card/Kconfig index 79d8212..ae6c60b 100644 --- a/drivers/mmc/card/Kconfig +++ b/drivers/mmc/card/Kconfig @@ -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. diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c index f925784..8b7931c 100644 --- a/drivers/mmc/card/block.c +++ b/drivers/mmc/card/block.c @@ -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); diff --git a/drivers/mmc/card/queue.h b/drivers/mmc/card/queue.h index 99e6521..e417903 100644 --- a/drivers/mmc/card/queue.h +++ b/drivers/mmc/card/queue.h @@ -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 *, -- 2.8.0.rc3.226.g39d4020 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html