Re: [RFC/PATCH] mmc: core: Add support for idle time BKOPs

[merez]

On Thu, August 30, 2012 12:36 am, Jaehoon Chung wrote:
> On 08/05/2012 10:08 PM, Maya Erez wrote:
>> When the mmcqd thread is idle, a delayed work is created to check the
>> need for BKOPs. The time to start the delayed work is calculated based
>> on the host controller suspend timeout, in case it was set. If not, a
>> default time is used.
>> If BKOPs is required in level 1, which is non-blocking, there will be
>> polling of the card status to wait for the BKOPs completion and prevent
>> suspend that will interrupt the BKOPs.
>> If the card raised an exception, the need for urgent BKOPs (level 2/3)
>> will be checked immediately and if needed, the BKOPs will be performed
>> without waiting for the next idle time.
>>
>> Signed-off-by: Maya Erez <merez@xxxxxxxxxxxxxx>
>> Signed-off-by: Jaehoon Chung <jh80.chung@xxxxxxxxxxx>
>> ---
>> This patch depends on the following patch:
>>   [PATCH v11] mmc: support BKOPS feature for eMMC
>>
>> This patch is based on the periodic BKOPs implementation in version 8 of
>> "support BKOPS feature for eMMC" patch.
>> The patch was modified to answer the following issues:
>> - In order to prevent a race condition between going into suspend and
>> starting BKOPs,
>>   the suspend timeout of the host controller is taking into accound in
>> determination of the start time
>>   of the delayed work
>> - Since mmc_start_bkops is called from two contexts now, mmc_claim_host
>> was moved to the beginning of the function
>> - Also, the check of doing_bkops should be protected when determing if
>> an HPI is needed due to the same reason.
>> - Starting and canceling the delayed work in each idle caused
>> degradation of iozone performance. Therefore,
>>   the delayed work is not started on each idle. Currently the number of
>> issued requests from the last delayed work
>>   is the trigger. We still investigate the best trigger for starting the
>> delayed work.
>> - To prevent degaradtion of iozone performance we also moved the call to
>> mmc_claim_host outside of mmc_stop_bkops
>>   and its release is done after issue_fn. This prevents an addition of a
>> full claim and release, that is also done
>>   in issue_fn for the first request after idle time.
>> ---
>>  drivers/mmc/card/block.c |    3 +
>>  drivers/mmc/card/queue.c |   20 +++++
>>  drivers/mmc/core/core.c  |  188
>> +++++++++++++++++++++++++++++++++++++++++++---
>>  drivers/mmc/core/host.c  |   24 ++++++
>>  include/linux/mmc/card.h |    3 +
>>  include/linux/mmc/core.h |    3 +
>>  include/linux/mmc/host.h |   25 ++++++
>>  7 files changed, 256 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index f1c84de..4519271 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -1268,6 +1268,9 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue
>> *mq, struct request *rqc)
>>  	if (!rqc && !mq->mqrq_prev->req)
>>  		return 0;
>>
>> +	if (rqc)
>> +		card->idle_bkops_rw_reqs_nr++;
>> +
>>  	do {
>>  		if (rqc) {
>>  			/*
>> diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
>> index e360a97..c9e1cee 100644
>> --- a/drivers/mmc/card/queue.c
>> +++ b/drivers/mmc/card/queue.c
>> @@ -51,6 +51,7 @@ static int mmc_queue_thread(void *d)
>>  {
>>  	struct mmc_queue *mq = d;
>>  	struct request_queue *q = mq->queue;
>> +	bool release_host = false;
>>
>>  	current->flags |= PF_MEMALLOC;
>>
>> @@ -66,13 +67,32 @@ static int mmc_queue_thread(void *d)
>>  		spin_unlock_irq(q->queue_lock);
>>
>>  		if (req || mq->mqrq_prev->req) {
>> +			/*
>> +			 * If this is the first request, BKOPs might be in
>> +			 * progress and needs to be stopped before issuing the
>> +			 * request
>> +			 * */
>> +			if (!mq->mqrq_prev->req &&
>> +			    mq->card->ext_csd.bkops_en &&
>> +			    mq->card->idle_bkops_rw_reqs_nr == 0) {
>> +				release_host = true;
>> +				mmc_claim_host(mq->card->host);
>> +				mmc_stop_bkops(mq->card);
>> +			}
>> +
>>  			set_current_state(TASK_RUNNING);
>>  			mq->issue_fn(mq, req);
>> +			if (release_host) {
>> +				release_host = false;
>> +				mmc_release_host(mq->card->host);
>> +			}
>>  		} else {
>>  			if (kthread_should_stop()) {
>>  				set_current_state(TASK_RUNNING);
>>  				break;
>>  			}
>> +
>> +			mmc_start_delayed_bkops(mq->card);
>>  			up(&mq->thread_sem);
>>  			schedule();
>>  			down(&mq->thread_sem);
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index ed2cc93..14830d4 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -46,6 +46,15 @@
>>   * operations the card has to perform
>>   */
>>  #define MMC_BKOPS_MAX_TIMEOUT	(4 * 60 * 1000) /* max time to wait in ms
>> */
>> +/* Polling timeout and interval for waiting on non-blocking BKOPs
>> completion */
>> +#define BKOPS_COMPLETION_POLLING_TIMEOUT 10000 /* in ms */
>> +#define BKOPS_COMPLETION_POLLING_INTERVAL 1000 /* in ms */
>> +/*
>> + * Since canceling the delayed work might have significant effect on
>> the
>> + * performance of small requests we won't queue the delayed work every
>> time
>> + * mmcqd thread is idle
>> + */
>> +#define BKOPS_MIN_REQS_TO_QUEUE_DELAYED_WORK 1000
> How did you get the minimum request number "1000"?
> Is this tunable value?
We tried several values to prevent degradation of iozone results and this
gave the best results.
We are still tuning this value and one of the options is to count the
number of write requests only (since read activity on the card won't
change the need for BKOPs).
>>
>>  static struct workqueue_struct *workqueue;
>>  static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
>> @@ -252,6 +261,37 @@ mmc_start_request(struct mmc_host *host, struct
>> mmc_request *mrq)
>>  }
>>
>>  /**
>> + *      mmc_start_delayed_bkops() - Start a delayed work to check for
>> the need
>> + *      of non urgent BKOPs
>> + *
>> + *      @card: MMC card to start BKOPS
>> + */
>> +void mmc_start_delayed_bkops(struct mmc_card *card)
>> +{
>> +	if (!card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
>> +		return;
> if mmc_card_doing_bkops or didn't support bkops, idle_bkops_rw_reqs_nr
> need to reset?
>> +
>> +	if (card->idle_bkops_rw_reqs_nr <
>> BKOPS_MIN_REQS_TO_QUEUE_DELAYED_WORK)
>> +		return;
>> +
>> +	pr_debug("%s: %s: queueing delayed_bkops_work", __func__,
>> +		 mmc_hostname(card->host));
> missed "\n"..almost missed the new line("\n") at pr_debug.
Will fix that.
>> +
>> +	card->idle_bkops_rw_reqs_nr = 0;
>> +
>> +	/*
>> +	 * cancel_delayed_bkops_work will prevent a race condition between
>> +	 * fetching a request by the queue_thread and the delayed work
>> +	 */
>> +	card->host->bkops_info.cancel_delayed_work = false;
>> +	queue_delayed_work(card->host->bkops_info. wq,
>> +			   &card->host->bkops_info.idle_time_dw,
>> +		   msecs_to_jiffies(
>> +			   card->host->bkops_info.time_to_start_bkops_ms));
>> +}
>> +EXPORT_SYMBOL(mmc_start_delayed_bkops);
>> +
>> +/**
>>   *	mmc_start_bkops - start BKOPS for supported cards
>>   *	@card: MMC card to start BKOPS
>>   *	@form_exception: A flags to indicate if this function was
>> @@ -268,23 +308,47 @@ void mmc_start_bkops(struct mmc_card *card, bool
>> from_exception)
>>  	bool use_busy_signal;
>>
>>  	BUG_ON(!card);
>> -
>> -	if (!card->ext_csd.bkops_en || mmc_card_doing_bkops(card))
>> +	if (!card->ext_csd.bkops_en)
>>  		return;
>>
>> +	mmc_claim_host(card->host);
>> +
>> +	if ((card->host->bkops_info.cancel_delayed_work) && !from_exception) {
>> +		pr_debug("%s: %s: cancel_delayed_work was set, exit",
>> +			 __func__, mmc_hostname(card->host));
>> +		card->host->bkops_info.cancel_delayed_work = false;
>> +		goto out;
>> +	}
>> +
>> +	if (mmc_card_doing_bkops(card)) {
>> +		pr_debug("%s: %s: already doing bkops, exit", __func__,
>> +			 mmc_hostname(card->host));
>> +		goto out;
>> +	}
>> +
>>  	err = mmc_read_bkops_status(card);
>>  	if (err) {
>> -		pr_err("%s: Didn't read bkops status : %d\n",
>> +		pr_err("%s: Error %d while reading bkops status\n",
>>  		       mmc_hostname(card->host), err);
>> -		return;
>> +		goto out;
>>  	}
>> -
>>  	if (!card->ext_csd.raw_bkops_status)
>> -		return;
>> +		goto out;
>>
>> -	if (card->ext_csd.raw_bkops_status < EXT_CSD_BKOPS_LEVEL_2
>> -	    && (from_exception))
>> -		return;
>> +	pr_info("%s: %s: card->ext_csd.raw_bkops_status = %d", __func__,
>> +		mmc_hostname(card->host), card->ext_csd.raw_bkops_status);
>> +
>> +	/*
>> +	 * If the function was called due to exception but there is no need
>> +	 * for urgent BKOPs, BKOPs will be performed by the delayed BKOPs
>> +	 * work, before going to suspend
>> +	 */
>> +	if ((card->ext_csd.raw_bkops_status < EXT_CSD_BKOPS_LEVEL_2)
>> +	    && (from_exception)) {
>> +		pr_debug("%s: %s: Level 1 from exception, exit", __func__,
>> +			 mmc_hostname(card->host));
>> +		goto out;
>> +	}
>>
>>  	mmc_claim_host(card->host);
>>  	if (card->ext_csd.raw_bkops_status >= EXT_CSD_BKOPS_LEVEL_2) {
>> @@ -308,13 +372,101 @@ void mmc_start_bkops(struct mmc_card *card, bool
>> from_exception)
>>  	 * bkops executed synchronously, otherwise
>>  	 * the operation is in progress
>>  	 */
>> -	if (!use_busy_signal)
>> +	if (!use_busy_signal) {
>>  		mmc_card_set_doing_bkops(card);
>> +		pr_debug("%s: %s: starting the polling thread", __func__,
>> +			 mmc_hostname(card->host));
>> +		card->host->bkops_info.exit_wait_on_completion = false;
>> +		queue_work(system_nrt_wq,
>> +			   &card->host->bkops_info.completion_polling);
>> +	}
>>  out:
>>  	mmc_release_host(card->host);
>> +
>>  }
>>  EXPORT_SYMBOL(mmc_start_bkops);
>>
>> +/**
>> + * mmc_bkops_completion_polling() - Poll on the card status to
>> + * wait for the non-blocking BKOPs completion
>> + * @work:	The completion polling work
>> + *
>> + * The on-going reading of the card status will prevent the card
>> + * from getting into suspend while it is in the middle of
>> + * performing BKOPs.
>> + * Since the non blocking BKOPs can be interrupted by a fetched
>> + * request we also check exit_wait_on_completion.
>> + */
>> +void mmc_bkops_completion_polling(struct work_struct *work)
>> +{
>> +	struct mmc_host *host = container_of(work, struct mmc_host,
>> +			bkops_info.completion_polling);
>> +	unsigned long timeout_jiffies = jiffies +
>> +		msecs_to_jiffies(BKOPS_COMPLETION_POLLING_TIMEOUT);
>> +	u32 status;
>> +	int err;
>> +
>> +	/*
>> +	 * Wait for the BKOPs to complete. Keep reading the status to prevent
>> +	 * the host from getting into suspend
>> +	 */
>> +	do {
>> +		mmc_claim_host(host);
>> +
>> +		if (host->bkops_info.exit_wait_on_completion ||
>> +			(!mmc_card_doing_bkops(host->card))) {
>> +			goto out;
>> +		}
>> +
>> +		err = mmc_send_status(host->card, &status);
>> +		if (err) {
>> +			pr_err("%s: error %d requesting status\n",
>> +			       mmc_hostname(host), err);
>> +			goto out;
>> +		}
>> +
>> +		/*
>> +		 * Some cards mishandle the status bits, so make sure to check
>> +		 * both the busy indication and the card state.
>> +		 */
>> +		if ((status & R1_READY_FOR_DATA) &&
>> +		    (R1_CURRENT_STATE(status) != R1_STATE_PRG)) {
>> +			pr_debug("%s: completed BKOPs, exit polling", __func__);
> missing "..\n". other pr_debug also missed.
Will fix that.
>> +			mmc_card_clr_doing_bkops(host->card);
>> +			goto out;
>> +		}
>> +
>> +		mmc_release_host(host);
>> +
>> +		/*
>> +		 * Sleep before checking the card status again to allow the
>> +		 * card to complete the BKOPs operation
>> +		 */
>> +		msleep(BKOPS_COMPLETION_POLLING_INTERVAL);
>> +	} while (time_before(jiffies, timeout_jiffies));
>> +
>> +	pr_debug("%s: exit polling due to timeout", __func__);
>> +
>> +	return;
>> +out:
>> +	mmc_release_host(host);
>> +}
>> +
>> +/**
>> + * mmc_start_idle_time_bkops() - check if a non urgent BKOPs is
>> + * needed
>> + * @work:	The idle time BKOPs work
>> + */
>> +void mmc_start_idle_time_bkops(struct work_struct *work)
>> +{
>> +	struct mmc_host *host = container_of(work, struct mmc_host,
>> +			bkops_info.idle_time_dw.work);
>> +
>> +	mmc_start_bkops(host->card, false);
>> +
>> +}
>> +EXPORT_SYMBOL(mmc_start_idle_time_bkops);
>> +
>>  static void mmc_wait_done(struct mmc_request *mrq)
>>  {
>>  	complete(&mrq->completion);
>> @@ -574,12 +726,28 @@ EXPORT_SYMBOL(mmc_wait_for_cmd);
>>   *	to allow rapid servicing of foreground operations,e.g. read/
>>   *	writes. Wait until the card comes out of the programming state
>>   *	to avoid errors in servicing read/write requests.
>> + *
>> + *      This function should be called when the host is claimed
>>   */
>>  int mmc_stop_bkops(struct mmc_card *card)
>>  {
>>  	int err = 0;
>>
>>  	BUG_ON(!card);
>> +
>> +	if (delayed_work_pending(&card->host->bkops_info.idle_time_dw))
>> +		cancel_delayed_work_sync(&card->host->bkops_info.idle_time_dw);
>> +
>> +	/*
>> +	 * Notify the delayed work to be cancelled, in case it was already
>> +	 * removed from the queue, but was not started yet
>> +	 */
>> +	card->host->bkops_info.cancel_delayed_work = true;
>> +
>> +	if (!mmc_card_doing_bkops(card))
>> +		return err;
>> +
>> +	card->host->bkops_info.exit_wait_on_completion = true;
>>  	err = mmc_interrupt_hpi(card);
>>
>>  	/*
>> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
>> index 597f189..d328191 100644
>> --- a/drivers/mmc/core/host.c
>> +++ b/drivers/mmc/core/host.c
>> @@ -27,6 +27,11 @@
>>  #include "core.h"
>>  #include "host.h"
>>
>> +/*
>> + * A default time for checking the need for non urgent BKOPs once MMC
>> thread
>> + * is idle.
>> + */
>> +#define MMC_IDLE_BKOPS_TIME_MS 2000
>>  #define cls_dev_to_mmc_host(d)	container_of(d, struct mmc_host,
>> class_dev)
>>
>>  static void mmc_host_classdev_release(struct device *dev)
>> @@ -336,6 +341,11 @@ struct mmc_host *mmc_alloc_host(int extra, struct
>> device *dev)
>>  	spin_lock_init(&host->lock);
>>  	init_waitqueue_head(&host->wq);
>>  	INIT_DELAYED_WORK(&host->detect, mmc_rescan);
>> +	host->bkops_info. wq = create_singlethread_workqueue("bkops_wq");
>> +	INIT_DELAYED_WORK(&host->bkops_info.idle_time_dw,
>> +			  mmc_start_idle_time_bkops);
>> +	INIT_WORK(&host->bkops_info.completion_polling,
>> +		  mmc_bkops_completion_polling);
>>  #ifdef CONFIG_PM
>>  	host->pm_notify.notifier_call = mmc_pm_notify;
>>  #endif
>> @@ -386,6 +396,20 @@ int mmc_add_host(struct mmc_host *host)
>>  #endif
>>  	mmc_host_clk_sysfs_init(host);
>>
>> +	/*
>> +	 * Calculate the time to start the BKOPs checking.
>> +	 * The idle time of the host controller should be taken into account
>> +	 * in order to prevent a race condition before starting BKOPs and
>> +	 * going into suspend.
>> +	 * If the host controller didn't set its idle time, a default value is
>> +	 * used.
>> +	 */
>> +	host->bkops_info.time_to_start_bkops_ms = MMC_IDLE_BKOPS_TIME_MS;
>> +	if (host->bkops_info.host_suspend_tout_ms)
>> +		host->bkops_info.time_to_start_bkops_ms = min(
>> +			host->bkops_info.time_to_start_bkops_ms,
>> +			host->bkops_info.host_suspend_tout_ms/2);
>> +
>>  	mmc_start_host(host);
>>  	register_pm_notifier(&host->pm_notify);
>>
>> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
>> index 342fe84..835d6c8 100644
>> --- a/include/linux/mmc/card.h
>> +++ b/include/linux/mmc/card.h
>> @@ -280,6 +280,9 @@ struct mmc_card {
>>  	struct dentry		*debugfs_root;
>>  	struct mmc_part	part[MMC_NUM_PHY_PARTITION]; /* physical partitions */
>>  	unsigned int    nr_parts;
>> +
>> +	/* num of read/write reqs since last BKOPs delayed work was queued */
>> +	unsigned int idle_bkops_rw_reqs_nr;
>>  };
>>
>>  /*
>> diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
>> index 9b9cdaf..665d345 100644
>> --- a/include/linux/mmc/core.h
>> +++ b/include/linux/mmc/core.h
>> @@ -145,6 +145,9 @@ extern int mmc_app_cmd(struct mmc_host *, struct
>> mmc_card *);
>>  extern int mmc_wait_for_app_cmd(struct mmc_host *, struct mmc_card *,
>>  	struct mmc_command *, int);
>>  extern void mmc_start_bkops(struct mmc_card *card, bool
>> from_exception);
>> +extern void mmc_start_delayed_bkops(struct mmc_card *card);
>> +extern void mmc_start_idle_time_bkops(struct work_struct *work);
>> +extern void mmc_bkops_completion_polling(struct work_struct *work);
>>  extern int __mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int,
>> bool);
>>  extern int mmc_switch(struct mmc_card *, u8, u8, u8, unsigned int);
>>
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index f578a71..8aaaf1d 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> @@ -176,6 +176,29 @@ struct mmc_supply {
>>  	struct regulator *vqmmc;	/* Optional Vccq supply */
>>  };
>>
>> +/**
>> + * struct mmc_bkops_info - BKOPs data
>> + * @wq:			workqueue
>> + * @idle_time_dw:	Idle time bkops delayed work
>> + * @host_suspend_tout_ms:	The host controller idle time,
>> + *         before getting into suspend
>> + * @time_to_start_bkops_ms:	The time to start the BKOPs
>> + *		  delayed work once MMC thread is idle
>> + * @completion_polling:	Poll on BKOPs completion
>> + * @cancel_delayed_work: A flag to indicate if the delayed work
>> + *	       should be cancelled
>> + * @exit_wait_on_completion:  Exit flag for non blocking BKOPs
>> + */
>> +struct mmc_bkops_info {
>> +	struct workqueue_struct *wq;
>> +	struct delayed_work	idle_time_dw;
>> +	unsigned int		host_suspend_tout_ms;
>> +	unsigned int		time_to_start_bkops_ms;
>> +	struct work_struct	completion_polling;
>> +	bool			cancel_delayed_work;
>> +	bool			exit_wait_on_completion;
>> +};
>> +
>>  struct mmc_host {
>>  	struct device		*parent;
>>  	struct device		class_dev;
>> @@ -340,6 +363,8 @@ struct mmc_host {
>>
>>  	unsigned int		actual_clock;	/* Actual HC clock rate */
>>
>> +	struct mmc_bkops_info	bkops_info;
>> +
>>  	unsigned long		private[0] ____cacheline_aligned;
>>  };
>>
>>
>
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>
Thanks,
Maya

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