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Groups > linux.kernel > #1700855

[PATCH v2 11/16] dmaengine: bcm-sba-raid: Peek mbox when we have no free requests

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When setting up RAID array on several NVMe disks we observed that
sba_alloc_request() start failing (due to no free requests left)
and RAID array setup becomes very slow.

To improve performance, we do mbox channel peek when we have
no free requests. This improves performance of RAID array setup
because mbox requests that were completed but not processed by
mbox completion worker will be processed immediately by mbox
channel peek.

Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
---
 drivers/dma/bcm-sba-raid.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
index f14ed0a..399250e 100644
--- a/drivers/dma/bcm-sba-raid.c
+++ b/drivers/dma/bcm-sba-raid.c
@@ -200,6 +200,14 @@ static inline u32 __pure sba_cmd_pq_c_mdata(u32 d, u32 b1, u32 b0)
 
 /* ====== General helper routines ===== */
 
+static void sba_peek_mchans(struct sba_device *sba)
+{
+	int mchan_idx;
+
+	for (mchan_idx = 0; mchan_idx < sba->mchans_count; mchan_idx++)
+		mbox_client_peek_data(sba->mchans[mchan_idx]);
+}
+
 static struct sba_request *sba_alloc_request(struct sba_device *sba)
 {
 	unsigned long flags;
@@ -211,8 +219,17 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
 	if (req)
 		list_move_tail(&req->node, &sba->reqs_alloc_list);
 	spin_unlock_irqrestore(&sba->reqs_lock, flags);
-	if (!req)
+
+	if (!req) {
+		/*
+		 * We have no more free requests so, we peek
+		 * mailbox channels hoping few active requests
+		 * would have completed which will create more
+		 * room for new requests.
+		 */
+		sba_peek_mchans(sba);
 		return NULL;
+	}
 
 	req->flags = SBA_REQUEST_STATE_ALLOCED;
 	req->first = req;
@@ -560,17 +577,15 @@ static enum dma_status sba_tx_status(struct dma_chan *dchan,
 				     dma_cookie_t cookie,
 				     struct dma_tx_state *txstate)
 {
-	int mchan_idx;
 	enum dma_status ret;
 	struct sba_device *sba = to_sba_device(dchan);
 
-	for (mchan_idx = 0; mchan_idx < sba->mchans_count; mchan_idx++)
-		mbox_client_peek_data(sba->mchans[mchan_idx]);
-
 	ret = dma_cookie_status(dchan, cookie, txstate);
 	if (ret == DMA_COMPLETE)
 		return ret;
 
+	sba_peek_mchans(sba);
+
 	return dma_cookie_status(dchan, cookie, txstate);
 }
 
-- 
2.7.4

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[PATCH v2 00/16] Broadcom SBA-RAID driver improvements Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:40 +0200
  [PATCH v2 03/16] dmaengine: bcm-sba-raid: Common flags for sba_request state and fence Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:40 +0200
  [PATCH v2 08/16] dmaengine: bcm-sba-raid: Increase number of free sba_request Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:40 +0200
  [PATCH v2 05/16] dmaengine: bcm-sba-raid: Remove redundant resp_dma from sba_request Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:40 +0200
  [PATCH v2 12/16] dmaengine: bcm-sba-raid: Pre-ack async tx descriptor Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 10/16] dmaengine: bcm-sba-raid: Alloc resources before registering DMA device Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 14/16] dmaengine: bcm-sba-raid: Remove redundant SBA_REQUEST_STATE_RECEIVED Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 16/16] dmaengine: bcm-sba-raid: Explicitly ACK mailbox message after sending Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 13/16] dmaengine: bcm-sba-raid: Re-factor sba_process_deferred_requests() Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 15/16] dmaengine: bcm-sba-raid: Add debugfs support Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200
  [PATCH v2 11/16] dmaengine: bcm-sba-raid: Peek mbox when we have no free requests Anup Patel <anup.patel@broadcom.com> - 2017-08-01 12:50 +0200

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