Messages in this thread Patch in this message | | | From | Li Yang-R58472 <> | Subject | RE: [PATCH] fsldma: fix performance degradation by optimizing spinlock use. | Date | Thu, 26 Apr 2012 02:59:15 +0000 |
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Hi Dan and Vinod,
Please help to pick this patch up. It addresses a great performance regression for RAID offloading.
Acked-by: Li Yang <leoli@freescale.com>
- Leo
> -----Original Message----- > From: Shi Xuelin-B29237 > Sent: Thursday, April 26, 2012 10:04 AM > To: dan.j.williams@intel.com > Cc: vinod.koul@intel.com; linuxppc-dev@lists.ozlabs.org; linux- > kernel@vger.kernel.org; Ira W. Snyder; Li Yang-R58472 > Subject: RE: [PATCH] fsldma: fix performance degradation by optimizing > spinlock use. > > Hi Dan Williams, > > Do you have any comment about this patch? > > Thanks, > Forrest > > -----Original Message----- > From: Ira W. Snyder [mailto:iws@ovro.caltech.edu] > Sent: 2012年1月12日 0:14 > To: Shi Xuelin-B29237 > Cc: vinod.koul@intel.com; dan.j.williams@intel.com; linuxppc- > dev@lists.ozlabs.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] fsldma: fix performance degradation by optimizing > spinlock use. > > On Wed, Jan 11, 2012 at 07:54:55AM +0000, Shi Xuelin-B29237 wrote: > > Hello Iris, > > > > As we discussed in the previous patch, I add one smp_mb() in > fsl_tx_status. > > In my testing with iozone, this smp_mb() could cause 1%~2% performance > degradation. > > Anyway it is acceptable for me. Do you have any other comments? > > > > This patch looks fine to me. > > Ira > > > -----Original Message----- > > From: Shi Xuelin-B29237 > > Sent: 2011年12月26日 14:01 > > To: iws@ovro.caltech.edu; vinod.koul@intel.com; > dan.j.williams@intel.com; linuxppc-dev@lists.ozlabs.org; linux- > kernel@vger.kernel.org > > Cc: Shi Xuelin-B29237 > > Subject: [PATCH] fsldma: fix performance degradation by optimizing > spinlock use. > > > > From: Forrest shi <b29237@freescale.com> > > > > 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 <xuelin.shi@freescale.com> > > --- > > 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 > > > >
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