From: "Ira W. Snyder" <iws@ovro•caltech.edu>
To: Shi Xuelin-B29237 <B29237@freescale•com>
Cc: "vinod.koul@intel•com" <vinod.koul@intel•com>,
"dan.j.williams@intel•com" <dan.j.williams@intel•com>,
"linuxppc-dev@lists•ozlabs.org" <linuxppc-dev@lists•ozlabs.org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>
Subject: Re: [PATCH] fsldma: fix performance degradation by optimizing spinlock use.
Date: Wed, 11 Jan 2012 08:13:47 -0800 [thread overview]
Message-ID: <20120111161347.GA1430@ovro.caltech.edu> (raw)
In-Reply-To: <DBB740589CE8814680DECFE34BE197AB1665A3@039-SN1MPN1-006.039d.mgd.msft.net>
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
>
>
next prev parent reply other threads:[~2012-01-11 16:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-26 6:01 [PATCH] fsldma: fix performance degradation by optimizing spinlock use b29237
2012-01-11 7:54 ` Shi Xuelin-B29237
2012-01-11 16:13 ` Ira W. Snyder [this message]
2012-04-26 2:03 ` Shi Xuelin-B29237
2012-04-26 2:59 ` Li Yang-R58472
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120111161347.GA1430@ovro.caltech.edu \
--to=iws@ovro$(echo .)caltech.edu \
--cc=B29237@freescale$(echo .)com \
--cc=dan.j.williams@intel$(echo .)com \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=vinod.koul@intel$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox