Hi, Konstantin.
I added comments more below.
On Wednesday, December 12, 2012, Seungwon Jeon wrote:
> On Monday, December 10, 2012, Konstantin Dorfman wrote:
> > When current request is running on the bus and if next request fetched
> > by mmcqd is NULL, mmc context (mmcqd thread) gets blocked until the
> > current request completes. This means if new request comes in while
> > the mmcqd thread is blocked, this new request can not be prepared in
> > parallel to current ongoing request. This may result in latency to
> > start new request.
> >
> > This change allows to wake up the MMC thread (which
> > is waiting for the current running request to complete). Now once the
> > MMC thread is woken up, new request can be fetched and prepared in
> > parallel to current running request which means this new request can
> > be started immediately after the current running request completes.
> >
> > With this change read throughput is improved by 16%.
> >
> > Signed-off-by: Konstantin Dorfman <kdorfman@xxxxxxxxxxxxxx>
> > ---
> >
> >
> > v4:
> > keeps new synchronization mechanism within mmc/core
> > layer, so mmc/core external API's are not changed.
> > - context_info moved into mmc_host struct
> > - context_info initialized in mmc_rescan_try_freq()
> >
> > v3:
> > - new MMC_QUEUE_NEW_REQUEST flag to mark new request case
> > - lock added to update is_new_req flag
> > - condition for sending new req notification changed
> > - Moved start waiting for new req notification after fetching NULL
> > v2:
> > - Removed synchronization flags
> > - removed lock from done()
> > - flags names changed
> > v1:
> > - Initial submit
> >
> > drivers/mmc/card/block.c | 25 +++++------
> > drivers/mmc/card/queue.c | 27 ++++++++++-
> > drivers/mmc/card/queue.h | 2 +
> > drivers/mmc/core/core.c | 112 ++++++++++++++++++++++++++++++++++++++++++++-
> > include/linux/mmc/card.h | 12 +++++
> > include/linux/mmc/core.h | 3 +-
> > include/linux/mmc/host.h | 16 +++++++
> > 7 files changed, 177 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> > index 21056b9..6fe0412 100644
> > --- a/drivers/mmc/card/block.c
> > +++ b/drivers/mmc/card/block.c
> > @@ -113,17 +113,6 @@ struct mmc_blk_data {
> >
> > static DEFINE_MUTEX(open_lock);
> >
> > -enum mmc_blk_status {
> > - MMC_BLK_SUCCESS = 0,
> > - MMC_BLK_PARTIAL,
> > - MMC_BLK_CMD_ERR,
> > - MMC_BLK_RETRY,
> > - MMC_BLK_ABORT,
> > - MMC_BLK_DATA_ERR,
> > - MMC_BLK_ECC_ERR,
> > - MMC_BLK_NOMEDIUM,
> > -};
> > -
> > module_param(perdev_minors, int, 0444);
> > MODULE_PARM_DESC(perdev_minors, "Minors numbers to allocate per device");
> >
> > @@ -1180,6 +1169,7 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
> > memset(brq, 0, sizeof(struct mmc_blk_request));
> > brq->mrq.cmd = &brq->cmd;
> > brq->mrq.data = &brq->data;
> > + brq->mrq.host = card->host;
> Above setting have been added at __mmc_start_data_req function in previous sending.
> Currently there is no setting for sdio. Considering sdio case, the former would be better.
>
> >
> > brq->cmd.arg = blk_rq_pos(req);
> > if (!mmc_card_blockaddr(card))
> > @@ -1363,9 +1353,12 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
> > areq = &mq->mqrq_cur->mmc_active;
> > } else
> > areq = NULL;
> > - areq = mmc_start_req(card->host, areq, (int *) &status);
> > - if (!areq)
> > + areq = mmc_start_req(card->host, areq, (int *)&status);
> > + if (!areq) {
> > + if (status == MMC_BLK_NEW_REQUEST)
> > + mq->flags |= MMC_QUEUE_NEW_REQUEST;
> > return 0;
> > + }
> >
> > mq_rq = container_of(areq, struct mmc_queue_req, mmc_active);
> > brq = &mq_rq->brq;
> > @@ -1374,6 +1367,8 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
> > mmc_queue_bounce_post(mq_rq);
> >
> > switch (status) {
> > + case MMC_BLK_NEW_REQUEST:
> > + BUG(); /* should never get here */
Is there any case to reach here?
I didn't find it.
> > case MMC_BLK_SUCCESS:
> > case MMC_BLK_PARTIAL:
> > /*
> > @@ -1486,6 +1481,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
> > goto out;
> > }
> >
> > + mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
> > if (req && req->cmd_flags & REQ_DISCARD) {
> > /* complete ongoing async transfer before issuing discard */
> > if (card->host->areq)
> > @@ -1505,9 +1501,10 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
> > }
> >
> > out:
> > - if (!req)
> > + if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST))
> > /* release host only when there are no more requests */
> > mmc_release_host(card->host);
> > +
> > return ret;
> > }
> >
> > diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
> > index fadf52e..0c37b49 100644
> > --- a/drivers/mmc/card/queue.c
> > +++ b/drivers/mmc/card/queue.c
> > @@ -22,7 +22,6 @@
> >
> > #define MMC_QUEUE_BOUNCESZ 65536
> >
> > -#define MMC_QUEUE_SUSPENDED (1 << 0)
> >
> > /*
> > * Prepare a MMC request. This just filters out odd stuff.
> > @@ -63,11 +62,20 @@ static int mmc_queue_thread(void *d)
> > set_current_state(TASK_INTERRUPTIBLE);
> > req = blk_fetch_request(q);
> > mq->mqrq_cur->req = req;
> > + if (!req && mq->mqrq_prev->req &&
> > + !(mq->mqrq_prev->req->cmd_flags & REQ_FLUSH) &&
> > + !(mq->mqrq_prev->req->cmd_flags & REQ_DISCARD))
> > + mq->card->host->context_info.is_waiting_last_req = true;
> > +
Unlike normal R/W request, request for discard/flush will be finished synchronously.
That means blk_end_request is called with 1's cycle of 'issue_fn' and request will be freed in block layer.
Currently 'mqrq_prev->req' is keeping these request and is used above condition.
Maybe, same area may be reallocated for normal R/W request after discard/flush is finished.
But we still expect discard or flush is saved in 'mq->mqrq_prev->req'.
I wonder that 'mq->mqrq_prev->req' indicates the valid area in all case.
Thanks,
Seungwon Jeon
> > spin_unlock_irq(q->queue_lock);
> >
> > if (req || mq->mqrq_prev->req) {
> > set_current_state(TASK_RUNNING);
> > mq->issue_fn(mq, req);
> > + if (mq->flags & MMC_QUEUE_NEW_REQUEST) {
> > + mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
> > + continue; /* fetch again */
> > + }
> >
> > /*
> > * Current request becomes previous request
> > @@ -103,6 +111,8 @@ static void mmc_request_fn(struct request_queue *q)
> > {
> > struct mmc_queue *mq = q->queuedata;
> > struct request *req;
> > + unsigned long flags;
> > + struct mmc_context_info *cntx;
> >
> > if (!mq) {
> > while ((req = blk_fetch_request(q)) != NULL) {
> > @@ -112,7 +122,20 @@ static void mmc_request_fn(struct request_queue *q)
> > return;
> > }
> >
> > - if (!mq->mqrq_cur->req && !mq->mqrq_prev->req)
> > + cntx = &mq->card->host->context_info;
> > + if (!mq->mqrq_cur->req && mq->mqrq_prev->req) {
> > + /*
> > + * New MMC request arrived when MMC thread may be
> > + * blocked on the previous request to be complete
> > + * with no current request fetched
> > + */
> > + spin_lock_irqsave(&cntx->lock, flags);
> > + if (cntx->is_waiting_last_req) {
> > + cntx->is_new_req = true;
> > + wake_up_interruptible(&cntx->wait);
> > + }
> > + spin_unlock_irqrestore(&cntx->lock, flags);
> > + } else if (!mq->mqrq_cur->req && !mq->mqrq_prev->req)
> > wake_up_process(mq->thread);
> > }
> >
> > diff --git a/drivers/mmc/card/queue.h b/drivers/mmc/card/queue.h
> > index d2a1eb4..970d9e7 100644
> > --- a/drivers/mmc/card/queue.h
> > +++ b/drivers/mmc/card/queue.h
> > @@ -26,6 +26,8 @@ struct mmc_queue {
> > struct mmc_card *card;
> > struct task_struct *thread;
> > struct semaphore thread_sem;
> > +#define MMC_QUEUE_SUSPENDED (1 << 0)
> > +#define MMC_QUEUE_NEW_REQUEST (1 << 1)
> > unsigned int flags;
> > int (*issue_fn)(struct mmc_queue *, struct request *);
> > void *data;
> > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > index aaed768..344cd3a 100644
> > --- a/drivers/mmc/core/core.c
> > +++ b/drivers/mmc/core/core.c
> > @@ -319,11 +319,43 @@ out:
> > }
> > EXPORT_SYMBOL(mmc_start_bkops);
> >
> > +/*
> > + * mmc_wait_data_done() - done callback for data request
> > + * @mrq: done data request
> > + *
> > + * Wakes up mmc context, passed as callback to host controller driver
> > + */
> > +static void mmc_wait_data_done(struct mmc_request *mrq)
> > +{
> > + mrq->host->context_info.is_done_rcv = true;
> > + wake_up_interruptible(&mrq->host->context_info.wait);
> > +}
> > +
> > static void mmc_wait_done(struct mmc_request *mrq)
> > {
> > complete(&mrq->completion);
> > }
> >
> > +/*
> > + *__mmc_start_data_req() - starts data request
> > + * @host: MMC host to start the request
> > + * @mrq: data request to start
> > + *
> > + * Fills done callback that will be used when request are done by card.
> > + * Starts data mmc request execution
> > + */
> > +static int __mmc_start_data_req(struct mmc_host *host, struct mmc_request *mrq)
> > +{
> > + mrq->done = mmc_wait_data_done;
> > + if (mmc_card_removed(host->card)) {
> > + mrq->cmd->error = -ENOMEDIUM;
> > + return -ENOMEDIUM;
> > + }
> > + mmc_start_request(host, mrq);
> > +
> > + return 0;
> > +}
> > +
> > static int __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)
> > {
> > init_completion(&mrq->completion);
> > @@ -337,6 +369,60 @@ static int __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)
> > return 0;
> > }
> >
> > +/*
> > + * mmc_wait_for_data_req_done() - wait for request completed or new
> > + * request notification arrives
> > + * @host: MMC host to prepare the command.
> > + * @mrq: MMC request to wait for
> > + *
> > + * Blocks MMC context till host controller will ack end of data request
> > + * execution or new request arrives from block layer. Handles
> > + * command retries.
> > + *
> > + * Returns enum mmc_blk_status after checking errors.
> > + */
> > +static int mmc_wait_for_data_req_done(struct mmc_host *host,
> > + struct mmc_request *mrq)
> > +{
> > + struct mmc_command *cmd;
> > + struct mmc_context_info *context_info = &host->context_info;
> > + int err;
> > + unsigned long flags;
> > +
> > + while (1) {
> > + wait_event_interruptible(context_info->wait,
> > + (context_info->is_done_rcv ||
> > + context_info->is_new_req));
> > + spin_lock_irqsave(&context_info->lock, flags);
> > + context_info->is_waiting_last_req = false;
> > + spin_unlock_irqrestore(&context_info->lock, flags);
> > + if (context_info->is_done_rcv) {
> > + context_info->is_done_rcv = false;
> > + context_info->is_new_req = false;
> > + cmd = mrq->cmd;
> > + if (!cmd->error || !cmd->retries ||
> > + mmc_card_removed(host->card)) {
> > + err = host->areq->err_check(host->card,
> > + host->areq);
> > + break; /* return err */
> > + } else {
> > + pr_info("%s: req failed (CMD%u): %d, retrying...\n",
> > + mmc_hostname(host),
> > + cmd->opcode, cmd->error);
> > + cmd->retries--;
> > + cmd->error = 0;
> > + host->ops->request(host, mrq);
> > + continue; /* wait for done/new event again */
> > + }
> > + } else if (context_info->is_new_req) {
> > + context_info->is_new_req = false;
> > + err = MMC_BLK_NEW_REQUEST;
> > + break; /* return err */
> > + }
> > + } /* while */
> > + return err;
> > +}
> > +
> > static void mmc_wait_for_req_done(struct mmc_host *host,
> > struct mmc_request *mrq)
> > {
> > @@ -426,8 +512,21 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
> > mmc_pre_req(host, areq->mrq, !host->areq);
> >
> > if (host->areq) {
> > - mmc_wait_for_req_done(host, host->areq->mrq);
> > - err = host->areq->err_check(host->card, host->areq);
> > + err = mmc_wait_for_data_req_done(host, host->areq->mrq);
> > + if (err == MMC_BLK_NEW_REQUEST) {
> > + if (areq) {
> > + pr_err("%s: new request while areq = %p",
> > + mmc_hostname(host), areq);
> > + BUG_ON(1);
> > + }
> > + if (error)
> > + *error = err;
> > + /*
> > + * The previous request was not completed,
> > + * nothing to return
> > + */
> > + return NULL;
> > + }
> > /*
> > * Check BKOPS urgency for each R1 response
> > */
> > @@ -439,7 +538,7 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
> > }
> >
> > if (!err && areq)
> > - start_err = __mmc_start_req(host, areq->mrq);
> > + start_err = __mmc_start_data_req(host, areq->mrq);
> >
> > if (host->areq)
> > mmc_post_req(host, host->areq->mrq, 0);
> > @@ -455,6 +554,7 @@ struct mmc_async_req *mmc_start_req(struct mmc_host *host,
> >
> > if (error)
> > *error = err;
> > +
> > return data;
> > }
> > EXPORT_SYMBOL(mmc_start_req);
> > @@ -2086,6 +2186,12 @@ static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
> >
> > mmc_send_if_cond(host, host->ocr_avail);
> >
> > + spin_lock_init(&host->context_info.lock);
> > + host->context_info.is_new_req = false;
> > + host->context_info.is_done_rcv = false;
> > + host->context_info.is_waiting_last_req = false;
> > + init_waitqueue_head(&host->context_info.wait);
> > +
> This path may be retired when mmc_rescan_try_freq is failed.
> How about putting these in mmc_add_card(mmc/core/bus.c)
> <Quote>
> ret = device_add(&card->dev);
> if (ret)
> return ret;
> -> Here seems good point.
>
> mmc_card_set_present(card);
> </Quote>
> Thanks,
> Seungwon Jeon
>
> > /* Order's important: probe SDIO, then SD, then MMC */
> > if (!mmc_attach_sdio(host))
> > return 0;
> > diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> > index 5c69315..be2500a 100644
> > --- a/include/linux/mmc/card.h
> > +++ b/include/linux/mmc/card.h
> > @@ -187,6 +187,18 @@ struct sdio_func_tuple;
> >
> > #define SDIO_MAX_FUNCS 7
> >
> > +enum mmc_blk_status {
> > + MMC_BLK_SUCCESS = 0,
> > + MMC_BLK_PARTIAL,
> > + MMC_BLK_CMD_ERR,
> > + MMC_BLK_RETRY,
> > + MMC_BLK_ABORT,
> > + MMC_BLK_DATA_ERR,
> > + MMC_BLK_ECC_ERR,
> > + MMC_BLK_NOMEDIUM,
> > + MMC_BLK_NEW_REQUEST,
> > +};
> > +
> > /* The number of MMC physical partitions. These consist of:
> > * boot partitions (2), general purpose partitions (4) in MMC v4.4.
> > */
> > diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
> > index 5bf7c22..724cc95 100644
> > --- a/include/linux/mmc/core.h
> > +++ b/include/linux/mmc/core.h
> > @@ -120,6 +120,7 @@ struct mmc_data {
> > s32 host_cookie; /* host private data */
> > };
> >
> > +struct mmc_host;
> > struct mmc_request {
> > struct mmc_command *sbc; /* SET_BLOCK_COUNT for multiblock */
> > struct mmc_command *cmd;
> > @@ -128,9 +129,9 @@ struct mmc_request {
> >
> > struct completion completion;
> > void (*done)(struct mmc_request *);/* completion function */
> > + struct mmc_host *host;
> > };
> >
> > -struct mmc_host;
> > struct mmc_card;
> > struct mmc_async_req;
> >
> > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> > index 61a10c1..c26c180 100644
> > --- a/include/linux/mmc/host.h
> > +++ b/include/linux/mmc/host.h
> > @@ -177,6 +177,21 @@ struct mmc_supply {
> > struct regulator *vqmmc; /* Optional Vccq supply */
> > };
> >
> > +/**
> > + * mmc_context_info - synchronization details for mmc context
> > + * @is_done_rcv wake up reason was done request
> > + * @is_new_req wake up reason was new request
> > + * @is_waiting_last_req mmc context waiting for single running request
> > + * @wait wait queue
> > + */
> > +struct mmc_context_info {
> > + bool is_done_rcv;
> > + bool is_new_req;
> > + bool is_waiting_last_req;
> > + wait_queue_head_t wait;
> > + spinlock_t lock;
> > +};
> > +
> > struct mmc_host {
> > struct device *parent;
> > struct device class_dev;
> > @@ -331,6 +346,7 @@ struct mmc_host {
> > struct dentry *debugfs_root;
> >
> > struct mmc_async_req *areq; /* active async req */
> > + struct mmc_context_info context_info; /* async synchronization info */
> >
> > #ifdef CONFIG_FAIL_MMC_REQUEST
> > struct fault_attr fail_mmc_request;
> > --
> > 1.7.6
> > --
> > Konstantin Dorfman,
> > QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center,
> > Inc. is a member of Code Aurora Forum,
> > hosted by The Linux Foundation
> > --
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