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SubjectRe: [PATCH v2 11/16] dmaengine: bcm-sba-raid: Peek mbox when we have no free requests
On Tue, Aug 01, 2017 at 04:07:55PM +0530, Anup Patel wrote:
> 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);

why do you want to do this while checking status..?

--
~Vinod

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