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: i...@ovro.caltech.edu; vinod.k...@intel.com; dan.j.willi...@intel.com; > linuxppc-dev@lists.ozlabs.org; linux-ker...@vger.kernel.org > Cc: Shi Xuelin-B29237 > Subject: [PATCH] fsldma: fix performance degradation by optimizing spinlock > use. > > From: Forrest shi <b29...@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....@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 > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
