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SubjectRe: [PATCH v2 09/16] dmaengine: bcm-sba-raid: Improve sba_issue_pending() run duration
On Tue, Aug 01, 2017 at 04:07:53PM +0530, Anup Patel wrote:
> The pending sba_request list can become very long in real-life usage
> (e.g. setting up RAID array) which can cause sba_issue_pending() to
> run for long duration.

that raises the warning flags.. Even if we have a long pending list why
would issue_pending run for long. The purpose of the issue_pending() is to
submit a txn if idle and return. The interrupt and tasklet shall push the
subsequent txn to hardware...


>
> This patch adds common sba_process_deferred_requests() to process
> few completed and pending requests so that it finishes in short
> duration. We use this common sba_process_deferred_requests() in
> both sba_issue_pending() and sba_receive_message().
>
> Signed-off-by: Anup Patel <anup.patel@broadcom.com>
> ---
> drivers/dma/bcm-sba-raid.c | 234 ++++++++++++++++++++++++---------------------
> 1 file changed, 125 insertions(+), 109 deletions(-)
>
> diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
> index af6cc8e..f6616da 100644
> --- a/drivers/dma/bcm-sba-raid.c
> +++ b/drivers/dma/bcm-sba-raid.c
> @@ -277,38 +277,28 @@ static void _sba_free_request(struct sba_device *sba,
> sba->reqs_fence = false;
> }
>
> -static void sba_received_request(struct sba_request *req)
> +/* Note: Must be called with sba->reqs_lock held */
> +static void _sba_complete_request(struct sba_device *sba,
> + struct sba_request *req)
> {
> - unsigned long flags;
> - struct sba_device *sba = req->sba;
> -
> - spin_lock_irqsave(&sba->reqs_lock, flags);
> + lockdep_assert_held(&sba->reqs_lock);
> req->flags &= ~SBA_REQUEST_STATE_MASK;
> - req->flags |= SBA_REQUEST_STATE_RECEIVED;
> - list_move_tail(&req->node, &sba->reqs_received_list);
> - spin_unlock_irqrestore(&sba->reqs_lock, flags);
> + req->flags |= SBA_REQUEST_STATE_COMPLETED;
> + list_move_tail(&req->node, &sba->reqs_completed_list);
> + if (list_empty(&sba->reqs_active_list))
> + sba->reqs_fence = false;
> }
>
> -static void sba_complete_chained_requests(struct sba_request *req)
> +/* Note: Must be called with sba->reqs_lock held */
> +static void _sba_received_request(struct sba_device *sba,
> + struct sba_request *req)
> {
> - unsigned long flags;
> - struct sba_request *nreq;
> - struct sba_device *sba = req->sba;
> -
> - spin_lock_irqsave(&sba->reqs_lock, flags);
> -
> + lockdep_assert_held(&sba->reqs_lock);
> req->flags &= ~SBA_REQUEST_STATE_MASK;
> - req->flags |= SBA_REQUEST_STATE_COMPLETED;
> - list_move_tail(&req->node, &sba->reqs_completed_list);
> - list_for_each_entry(nreq, &req->next, next) {
> - nreq->flags &= ~SBA_REQUEST_STATE_MASK;
> - nreq->flags |= SBA_REQUEST_STATE_COMPLETED;
> - list_move_tail(&nreq->node, &sba->reqs_completed_list);
> - }
> + req->flags |= SBA_REQUEST_STATE_RECEIVED;
> + list_move_tail(&req->node, &sba->reqs_received_list);
> if (list_empty(&sba->reqs_active_list))
> sba->reqs_fence = false;
> -
> - spin_unlock_irqrestore(&sba->reqs_lock, flags);
> }
>
> static void sba_free_chained_requests(struct sba_request *req)
> @@ -386,26 +376,6 @@ static void sba_cleanup_pending_requests(struct sba_device *sba)
> spin_unlock_irqrestore(&sba->reqs_lock, flags);
> }
>
> -/* ====== DMAENGINE callbacks ===== */
> -
> -static void sba_free_chan_resources(struct dma_chan *dchan)
> -{
> - /*
> - * Channel resources are pre-alloced so we just free-up
> - * whatever we can so that we can re-use pre-alloced
> - * channel resources next time.
> - */
> - sba_cleanup_nonpending_requests(to_sba_device(dchan));
> -}
> -
> -static int sba_device_terminate_all(struct dma_chan *dchan)
> -{
> - /* Cleanup all pending requests */
> - sba_cleanup_pending_requests(to_sba_device(dchan));
> -
> - return 0;
> -}
> -
> static int sba_send_mbox_request(struct sba_device *sba,
> struct sba_request *req)
> {
> @@ -431,17 +401,27 @@ static int sba_send_mbox_request(struct sba_device *sba,
> return 0;
> }
>
> -static void sba_issue_pending(struct dma_chan *dchan)
> +static void sba_process_deferred_requests(struct sba_device *sba)
> {
> int ret;
> + u32 count;
> unsigned long flags;
> - struct sba_request *req, *req1;
> - struct sba_device *sba = to_sba_device(dchan);
> + struct sba_request *req;
> + struct dma_async_tx_descriptor *tx;
>
> spin_lock_irqsave(&sba->reqs_lock, flags);
>
> - /* Process all pending request */
> - list_for_each_entry_safe(req, req1, &sba->reqs_pending_list, node) {
> + /* Count pending requests */
> + count = 0;
> + list_for_each_entry(req, &sba->reqs_pending_list, node)
> + count++;
> +
> + /* Process pending requests */
> + while (!list_empty(&sba->reqs_pending_list) && count) {
> + /* Get the first pending request */
> + req = list_first_entry(&sba->reqs_pending_list,
> + struct sba_request, node);
> +
> /* Try to make request active */
> if (!_sba_active_request(sba, req))
> break;
> @@ -456,11 +436,102 @@ static void sba_issue_pending(struct dma_chan *dchan)
> _sba_pending_request(sba, req);
> break;
> }
> +
> + count--;
> + }
> +
> + /* Count completed requests */
> + count = 0;
> + list_for_each_entry(req, &sba->reqs_completed_list, node)
> + count++;
> +
> + /* Process completed requests */
> + while (!list_empty(&sba->reqs_completed_list) && count) {
> + req = list_first_entry(&sba->reqs_completed_list,
> + struct sba_request, node);
> + list_del_init(&req->node);
> + tx = &req->tx;
> +
> + spin_unlock_irqrestore(&sba->reqs_lock, flags);
> +
> + WARN_ON(tx->cookie < 0);
> + if (tx->cookie > 0) {
> + dma_cookie_complete(tx);
> + dmaengine_desc_get_callback_invoke(tx, NULL);
> + dma_descriptor_unmap(tx);
> + tx->callback = NULL;
> + tx->callback_result = NULL;
> + }
> +
> + dma_run_dependencies(tx);
> +
> + spin_lock_irqsave(&sba->reqs_lock, flags);
> +
> + /* If waiting for 'ack' then move to completed list */
> + if (!async_tx_test_ack(&req->tx))
> + _sba_complete_request(sba, req);
> + else
> + _sba_free_request(sba, req);
> +
> + count--;
> }
>
> + /* Re-check pending and completed work */
> + count = 0;
> + if (!list_empty(&sba->reqs_pending_list) ||
> + !list_empty(&sba->reqs_completed_list))
> + count = 1;
> +
> spin_unlock_irqrestore(&sba->reqs_lock, flags);
> }
>
> +static void sba_process_received_request(struct sba_device *sba,
> + struct sba_request *req)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&sba->reqs_lock, flags);
> +
> + /* Mark request as received */
> + _sba_received_request(sba, req);
> +
> + /* Update request */
> + if (!atomic_dec_return(&req->first->next_pending_count))
> + _sba_complete_request(sba, req->first);
> + if (req->first != req)
> + _sba_free_request(sba, req);
> +
> + spin_unlock_irqrestore(&sba->reqs_lock, flags);
> +}
> +
> +/* ====== DMAENGINE callbacks ===== */
> +
> +static void sba_free_chan_resources(struct dma_chan *dchan)
> +{
> + /*
> + * Channel resources are pre-alloced so we just free-up
> + * whatever we can so that we can re-use pre-alloced
> + * channel resources next time.
> + */
> + sba_cleanup_nonpending_requests(to_sba_device(dchan));
> +}
> +
> +static int sba_device_terminate_all(struct dma_chan *dchan)
> +{
> + /* Cleanup all pending requests */
> + sba_cleanup_pending_requests(to_sba_device(dchan));
> +
> + return 0;
> +}
> +
> +static void sba_issue_pending(struct dma_chan *dchan)
> +{
> + struct sba_device *sba = to_sba_device(dchan);
> +
> + /* Process deferred requests */
> + sba_process_deferred_requests(sba);
> +}
> +
> static dma_cookie_t sba_tx_submit(struct dma_async_tx_descriptor *tx)
> {
> unsigned long flags;
> @@ -1382,40 +1453,10 @@ sba_prep_dma_pq(struct dma_chan *dchan, dma_addr_t *dst, dma_addr_t *src,
>
> /* ====== Mailbox callbacks ===== */
>
> -static void sba_dma_tx_actions(struct sba_request *req)
> -{
> - struct dma_async_tx_descriptor *tx = &req->tx;
> -
> - WARN_ON(tx->cookie < 0);
> -
> - if (tx->cookie > 0) {
> - dma_cookie_complete(tx);
> -
> - /*
> - * Call the callback (must not sleep or submit new
> - * operations to this channel)
> - */
> - if (tx->callback)
> - tx->callback(tx->callback_param);
> -
> - dma_descriptor_unmap(tx);
> - }
> -
> - /* Run dependent operations */
> - dma_run_dependencies(tx);
> -
> - /* If waiting for 'ack' then move to completed list */
> - if (!async_tx_test_ack(&req->tx))
> - sba_complete_chained_requests(req);
> - else
> - sba_free_chained_requests(req);
> -}
> -
> static void sba_receive_message(struct mbox_client *cl, void *msg)
> {
> - unsigned long flags;
> struct brcm_message *m = msg;
> - struct sba_request *req = m->ctx, *req1;
> + struct sba_request *req = m->ctx;
> struct sba_device *sba = req->sba;
>
> /* Error count if message has error */
> @@ -1423,36 +1464,11 @@ static void sba_receive_message(struct mbox_client *cl, void *msg)
> dev_err(sba->dev, "%s got message with error %d",
> dma_chan_name(&sba->dma_chan), m->error);
>
> - /* Mark request as received */
> - sba_received_request(req);
> -
> - /* Wait for all chained requests to be completed */
> - if (atomic_dec_return(&req->first->next_pending_count))
> - goto done;
> -
> - /* Point to first request */
> - req = req->first;
> -
> - /* Update request */
> - if (req->flags & SBA_REQUEST_STATE_RECEIVED)
> - sba_dma_tx_actions(req);
> - else
> - sba_free_chained_requests(req);
> -
> - spin_lock_irqsave(&sba->reqs_lock, flags);
> -
> - /* Re-check all completed request waiting for 'ack' */
> - list_for_each_entry_safe(req, req1, &sba->reqs_completed_list, node) {
> - spin_unlock_irqrestore(&sba->reqs_lock, flags);
> - sba_dma_tx_actions(req);
> - spin_lock_irqsave(&sba->reqs_lock, flags);
> - }
> -
> - spin_unlock_irqrestore(&sba->reqs_lock, flags);
> + /* Process received request */
> + sba_process_received_request(sba, req);
>
> -done:
> - /* Try to submit pending request */
> - sba_issue_pending(&sba->dma_chan);
> + /* Process deferred requests */
> + sba_process_deferred_requests(sba);
> }
>
> /* ====== Platform driver routines ===== */
> --
> 2.7.4
>

--
~Vinod

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