Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751647AbdHRLhG (ORCPT ); Fri, 18 Aug 2017 07:37:06 -0400 Received: from mail-ua0-f182.google.com ([209.85.217.182]:33602 "EHLO mail-ua0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993AbdHRLgr (ORCPT ); Fri, 18 Aug 2017 07:36:47 -0400 MIME-Version: 1.0 In-Reply-To: <20170817064008.GB3053@localhost> References: <1501583880-32072-1-git-send-email-anup.patel@broadcom.com> <1501583880-32072-12-git-send-email-anup.patel@broadcom.com> <20170817064008.GB3053@localhost> From: Anup Patel Date: Fri, 18 Aug 2017 17:06:46 +0530 Message-ID: Subject: Re: [PATCH v2 11/16] dmaengine: bcm-sba-raid: Peek mbox when we have no free requests To: Vinod Koul Cc: Rob Herring , Mark Rutland , Dan Williams , Florian Fainelli , Scott Branden , Ray Jui , Linux Kernel , Linux ARM Kernel , Device Tree , dmaengine@vger.kernel.org, BCM Kernel Feedback Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3243 Lines: 86 On Thu, Aug 17, 2017 at 12:10 PM, Vinod Koul wrote: > 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 >> Reviewed-by: Ray Jui >> Reviewed-by: Scott Branden >> --- >> 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..? The dma_tx_state is only updated via sba_receive_message() which in-turn is called by mailbox framework upon completion of a request. Placing the sba_peek_mchans() here helps polling based DMA client by not waiting for IRQ worker to schedule and process the completions. Regards, Anup