Hi Chris, Can we push this change to mmc-next? Thanks, Maya On Mon, July 2, 2012 5:15 am, Maya Erez wrote: > The write packing control will ensure that read requests latency is > not increased due to long write packed commands. > > The trigger for enabling the write packing is managing to pack several > write requests. The number of potential packed requests that will trigger > the packing can be configured via sysfs by writing the required value to: > /sys/block/<block_dev_name>/num_wr_reqs_to_start_packing. > The trigger for disabling the write packing is fetching a read request. > > Signed-off-by: Maya Erez <merez@xxxxxxxxxxxxxx> > > diff --git a/Documentation/mmc/mmc-dev-attrs.txt > b/Documentation/mmc/mmc-dev-attrs.txt > index 22ae844..f4a48a8 100644 > --- a/Documentation/mmc/mmc-dev-attrs.txt > +++ b/Documentation/mmc/mmc-dev-attrs.txt > @@ -8,6 +8,23 @@ The following attributes are read/write. > > force_ro Enforce read-only access even if write protect switch is off. > > + num_wr_reqs_to_start_packing This attribute is used to determine > + the trigger for activating the write packing, in case the write > + packing control feature is enabled. > + > + When the MMC manages to reach a point where num_wr_reqs_to_start_packing > + write requests could be packed, it enables the write packing feature. > + This allows us to start the write packing only when it is beneficial > + and has minimum affect on the read latency. > + > + The number of potential packed requests that will trigger the packing > + can be configured via sysfs by writing the required value to: > + /sys/block/<block_dev_name>/mmc/num_wr_reqs_to_start_packing. > + > + The default value of num_wr_reqs_to_start_packing was determined by > + running parallel lmdd write and lmdd read operations and calculating > + the max number of packed writes requests. > + > SD and MMC Device Attributes > ============================ > > diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c > index c23034d..3d13d5f 100644 > --- a/drivers/mmc/card/block.c > +++ b/drivers/mmc/card/block.c > @@ -114,6 +114,7 @@ struct mmc_blk_data { > struct device_attribute force_ro; > struct device_attribute power_ro_lock; > int area_type; > + struct device_attribute num_wr_reqs_to_start_packing; > > struct kobject kobj; > struct kobj_type kobj_type; > @@ -329,6 +330,38 @@ out: > return ret; > } > > +static ssize_t > +num_wr_reqs_to_start_packing_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev)); > + int num_wr_reqs_to_start_packing; > + int ret; > + > + num_wr_reqs_to_start_packing = md->queue.num_wr_reqs_to_start_packing; > + > + ret = snprintf(buf, PAGE_SIZE, "%d\n", num_wr_reqs_to_start_packing); > + > + mmc_blk_put(md); > + return ret; > +} > + > +static ssize_t > +num_wr_reqs_to_start_packing_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)); > + > + sscanf(buf, "%d", &value); > + if (value >= 0) > + md->queue.num_wr_reqs_to_start_packing = value; > + > + mmc_blk_put(md); > + return count; > +} > + > static int mmc_blk_open(struct block_device *bdev, fmode_t mode) > { > struct mmc_blk_data *md = mmc_blk_get(bdev->bd_disk); > @@ -1344,6 +1377,49 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req > *mqrq, > mmc_queue_bounce_pre(mqrq); > } > > +static void mmc_blk_write_packing_control(struct mmc_queue *mq, > + struct request *req) > +{ > + struct mmc_host *host = mq->card->host; > + int data_dir; > + > + if (!(host->caps2 & MMC_CAP2_PACKED_WR)) > + return; > + > + /* > + * In case the packing control is not supported by the host, it should > + * not have an effect on the write packing. Therefore we have to enable > + * the write packing > + */ > + if (!(host->caps2 & MMC_CAP2_PACKED_WR_CONTROL)) { > + mq->wr_packing_enabled = true; > + return; > + } > + > + if (!req || (req && (req->cmd_flags & REQ_FLUSH))) { > + if (mq->num_of_potential_packed_wr_reqs > > + mq->num_wr_reqs_to_start_packing) > + mq->wr_packing_enabled = true; > + mq->num_of_potential_packed_wr_reqs = 0; > + return; > + } > + > + data_dir = rq_data_dir(req); > + > + if (data_dir == READ) { > + mq->num_of_potential_packed_wr_reqs = 0; > + mq->wr_packing_enabled = false; > + return; > + } else if (data_dir == WRITE) { > + mq->num_of_potential_packed_wr_reqs++; > + } > + > + if (mq->num_of_potential_packed_wr_reqs > > + mq->num_wr_reqs_to_start_packing) > + mq->wr_packing_enabled = true; > + > +} > + > static u8 mmc_blk_prep_packed_list(struct mmc_queue *mq, struct request > *req) > { > struct request_queue *q = mq->queue; > @@ -1363,6 +1439,9 @@ static u8 mmc_blk_prep_packed_list(struct mmc_queue > *mq, struct request *req) > !card->ext_csd.packed_event_en) > goto no_packed; > > + if (!mq->wr_packing_enabled) > + goto no_packed; > + > if ((rq_data_dir(cur) == WRITE) && > (card->host->caps2 & MMC_CAP2_PACKED_WR)) > max_packed_rw = card->ext_csd.max_packed_writes; > @@ -1436,6 +1515,8 @@ static u8 mmc_blk_prep_packed_list(struct mmc_queue > *mq, struct request *req) > break; > } > > + if (rq_data_dir(next) == WRITE) > + mq->num_of_potential_packed_wr_reqs++; > list_add_tail(&next->queuelist, &mq->mqrq_cur->packed_list); > cur = next; > reqs++; > @@ -1821,7 +1902,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, > struct request *req) > goto out; > } > > - if (req && req->cmd_flags & REQ_DISCARD) { > + mmc_blk_write_packing_control(mq, req); > + > + if (req && req->cmd_flags & REQ_DISCARD) { > /* complete ongoing async transfer before issuing discard */ > if (card->host->areq) > mmc_blk_issue_rw_rq(mq, NULL); > @@ -2057,6 +2140,8 @@ static void mmc_blk_remove_req(struct mmc_blk_data > *md) > card->ext_csd.boot_ro_lockable) > sysfs_remove_file(&md->kobj, > &md->power_ro_lock.attr); > + sysfs_remove_file(&md->kobj, > + &md->num_wr_reqs_to_start_packing.attr); > > /* Stop new requests from getting into the queue */ > del_gendisk(md->disk); > @@ -2124,8 +2209,26 @@ static int mmc_add_disk(struct mmc_blk_data *md) > if (ret) > goto power_ro_lock_fail; > } > + > + md->num_wr_reqs_to_start_packing.show = > + num_wr_reqs_to_start_packing_show; > + md->num_wr_reqs_to_start_packing.store = > + num_wr_reqs_to_start_packing_store; > + sysfs_attr_init(&md->num_wr_reqs_to_start_packing.attr); > + md->num_wr_reqs_to_start_packing.attr.name = > + "num_wr_reqs_to_start_packing"; > + md->num_wr_reqs_to_start_packing.attr.mode = S_IRUGO | S_IWUSR; > + ret = sysfs_create_file(&md->kobj, > + &md->num_wr_reqs_to_start_packing.attr); > + if (ret) > + goto num_wr_reqs_to_start_packing_fail; > + > return ret; > > +num_wr_reqs_to_start_packing_fail: > + if ((md->area_type & MMC_BLK_DATA_AREA_BOOT) && > + card->ext_csd.boot_ro_lockable) > + sysfs_remove_file(&md->kobj, &md->power_ro_lock.attr); > power_ro_lock_fail: > sysfs_remove_file(&md->kobj, &md->force_ro.attr); > force_ro_fail: > diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c > index 165d85a..79ef91b 100644 > --- a/drivers/mmc/card/queue.c > +++ b/drivers/mmc/card/queue.c > @@ -25,6 +25,13 @@ > #define MMC_QUEUE_SUSPENDED (1 << 0) > > /* > + * Based on benchmark tests the default num of requests to trigger the > write > + * packing was determined, to keep the read latency as low as possible > and > + * manage to keep the high write throughput. > + */ > +#define DEFAULT_NUM_REQS_TO_START_PACK 17 > + > +/* > * Prepare a MMC request. This just filters out odd stuff. > */ > static int mmc_prep_request(struct request_queue *q, struct request *req) > @@ -181,6 +188,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct > mmc_card *card, > mq->mqrq_cur = mqrq_cur; > mq->mqrq_prev = mqrq_prev; > mq->queue->queuedata = mq; > + mq->num_wr_reqs_to_start_packing = DEFAULT_NUM_REQS_TO_START_PACK; > > blk_queue_prep_rq(mq->queue, mmc_prep_request); > queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mq->queue); > diff --git a/drivers/mmc/card/queue.h b/drivers/mmc/card/queue.h > index 5e04938..93e4b59 100644 > --- a/drivers/mmc/card/queue.h > +++ b/drivers/mmc/card/queue.h > @@ -45,6 +45,9 @@ struct mmc_queue { > struct mmc_queue_req mqrq[2]; > struct mmc_queue_req *mqrq_cur; > struct mmc_queue_req *mqrq_prev; > + bool wr_packing_enabled; > + int num_of_potential_packed_wr_reqs; > + int num_wr_reqs_to_start_packing; > }; > > extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, > spinlock_t *, > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h > index bb19b98..6a439ae 100644 > --- a/include/linux/mmc/host.h > +++ b/include/linux/mmc/host.h > @@ -249,6 +249,7 @@ struct mmc_host { > #define MMC_CAP2_PACKED_WR (1 << 11) /* Allow packed write */ > #define MMC_CAP2_PACKED_CMD (MMC_CAP2_PACKED_RD | \ > MMC_CAP2_PACKED_WR) /* Allow packed commands */ > +#define MMC_CAP2_PACKED_WR_CONTROL (1 << 12) /* Allow write packing > control */ > > mmc_pm_flag_t pm_caps; /* supported pm features */ > unsigned int power_notify_type; > -- > 1.7.3.3 > -- > Sent by a consultant of the Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. > -- Sent by consultant of Qualcomm Innovation Center, Inc. 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