From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751639Ab1LZGtm (ORCPT ); Mon, 26 Dec 2011 01:49:42 -0500 Received: from va3ehsobe006.messaging.microsoft.com ([216.32.180.16]:5390 "EHLO VA3EHSOBE007.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751330Ab1LZGth (ORCPT ); Mon, 26 Dec 2011 01:49:37 -0500 X-SpamScore: 0 X-BigFish: VS0(zzzz1202hzz8275bhz2dh2a8h668h839h) X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI From: To: , , , , CC: Forrest shi Subject: [PATCH] fsldma: fix performance degradation by optimizing spinlock use. Date: Mon, 26 Dec 2011 14:01:03 +0800 Message-ID: <1324879263-11845-1-git-send-email-b29237@freescale.com> X-Mailer: git-send-email 1.6.4 MIME-Version: 1.0 Content-Type: text/plain X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Forrest shi dma status check function fsl_tx_status is heavily called in a tight loop and the desc lock in fsl_tx_status contended by the dma status update function. this caused the dma performance degrades much. this patch releases the lock in the fsl_tx_status function, and introduce the smp_mb() to avoid possible memory inconsistency. Signed-off-by: Forrest Shi --- drivers/dma/fsldma.c | 6 +----- 1 files changed, 1 insertions(+), 5 deletions(-) diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c index 8a78154..008fb5e 100644 --- a/drivers/dma/fsldma.c +++ b/drivers/dma/fsldma.c @@ -986,15 +986,11 @@ static enum dma_status fsl_tx_status(struct dma_chan *dchan, struct fsldma_chan *chan = to_fsl_chan(dchan); dma_cookie_t last_complete; dma_cookie_t last_used; - unsigned long flags; - - spin_lock_irqsave(&chan->desc_lock, flags); last_complete = chan->completed_cookie; + smp_mb(); last_used = dchan->cookie; - spin_unlock_irqrestore(&chan->desc_lock, flags); - dma_set_tx_state(txstate, last_complete, last_used, 0); return dma_async_is_complete(cookie, last_complete, last_used); } -- 1.7.0.4