All of lore.kernel.org
 help / color / mirror / Atom feed
From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: David Brownell <david-b@pacbell.net>,
	linux-ide@vger.kernel.org,
	DaVinci <davinci-linux-open-source@linux.davincidsp.com>
Subject: Re: [patch 2.6.30-rc2 2/2] palm_bk3710:  UDMA performance fix
Date: Wed, 22 Apr 2009 20:26:10 +0200	[thread overview]
Message-ID: <200904222026.11495.bzolnier@gmail.com> (raw)
In-Reply-To: <49ED99AE.3020100@ru.mvista.com>

On Tuesday 21 April 2009 12:02:22 Sergei Shtylyov wrote:
> David Brownell wrote:
> 
> > Fix UDMA throughput bug:  tCYC averages t2CYCTYP/2, but the code
> > previously assumed it was the same as t2CYCTYP.
> 
>     Wow, thanks for finding it!
>     IIUC however, this should have only affected UDMA writes, not reads 
> because on reads the device controls the strobe timing.
> 
> > (That is, it was using just one clock edge, not both.)
> 
>     There's no way only one clock edge could have been used since it would 
> have resulted in CRC errors, so this comment is not to the point.
> 
> > On one system this change increased throughput by almost 4x: UDMA/66
> > sometimes topped 23 MB/sec (on a drive known to do much better).  On
> > another system it was around a 10% win (UDMA/66 up to 7+ MB/sec).
> 
>     It's interesting that on my DM6467 EVM UDMA/66 reads topped at about 29-30 
> MB/s even without this patch (measuread with hdparm), and on DM6446 EVM they 
> were only slightly slower...
> 
> > The difference might be caused by the ratio between memory and IDE
> > clocks.  In the system with large speedup, this was exactly 2 (as a
> > workaround for a rev 1.1 silicon bug).  The other system used a more
> > standard ratio of 1.63 (and rev 2.1 silicon) ... clock domain synch
> > might have some issues, they're not unheard-of.
> 
>     Interesting...
> 
> > Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
> 
>     The patch itself is:
> 
> Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>

applied

  parent reply	other threads:[~2009-04-22 18:45 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-21  1:41 [patch 2.6.30-rc2 2/2] palm_bk3710: UDMA performance fix David Brownell
2009-04-21 10:02 ` Sergei Shtylyov
     [not found]   ` <49ED99AE.3020100-hkdhdckH98+B+jHODAdFcQ@public.gmane.org>
2009-04-21 10:28     ` David Brownell
2009-04-22 18:26   ` Bartlomiej Zolnierkiewicz [this message]
2009-04-22 20:32     ` David Brownell
     [not found]     ` <200904222026.11495.bzolnier-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2009-04-22 20:43       ` David Brownell
2009-04-22 21:05         ` Bartlomiej Zolnierkiewicz
     [not found]           ` <200904222305.54820.bzolnier-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2009-04-22 22:29             ` David Brownell
2009-04-23 20:48               ` Bartlomiej Zolnierkiewicz

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=200904222026.11495.bzolnier@gmail.com \
    --to=bzolnier@gmail.com \
    --cc=david-b@pacbell.net \
    --cc=davinci-linux-open-source@linux.davincidsp.com \
    --cc=linux-ide@vger.kernel.org \
    --cc=sshtylyov@ru.mvista.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.