From: Eugene Surovegin <ebs@ebshome.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: debian-powerpc@lists.debian.org, linuxppc-dev@ozlabs.org
Subject: Re: Not coherent cache DMA for G3/G4 CPUs: clarification needed
Date: Thu, 20 Apr 2006 14:33:16 -0700 [thread overview]
Message-ID: <20060420213316.GD25755@gate.ebshome.net> (raw)
In-Reply-To: <1145567174.4517.1.camel@localhost.localdomain>
On Fri, Apr 21, 2006 at 07:06:13AM +1000, Benjamin Herrenschmidt wrote:
> (On 6xx this is deadly even if you don't access those cacheable pages
> because the CPU prefetch may do it for you).
Here is another thought if this "prefetch" theory is correct.
You guys seems to focus on
dma_alloc_coherent()/pci_alloc_consistent(), but forgeting about so
called "streaming" mappings.
You cannot just flush/invalidate cache any more, because "CPU can
prefetch this data back". So, to be completely correct (if you insist
on "6xx can prefetch"-theory), you have to actually _copy_ data to
your consistent memory on dma_map_single(). You can imagine
performance implications. I suspect even 440 will be faster in this
case than G4 :).
--
Eugene
next prev parent reply other threads:[~2006-04-20 21:33 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-20 18:57 Not coherent cache DMA for G3/G4 CPUs: clarification needed Gerhard Pircher
2006-04-20 20:38 ` Eugene Surovegin
2006-04-20 20:56 ` Gerhard Pircher
2006-04-20 21:02 ` Eugene Surovegin
2006-04-20 21:10 ` Gerhard Pircher
2006-04-20 21:55 ` Eugene Surovegin
2006-04-20 22:08 ` Gerhard Pircher
2006-04-24 19:21 ` Mark A. Greer
2006-04-21 4:38 ` Benjamin Herrenschmidt
2006-04-21 8:03 ` Gerhard Pircher
2006-04-21 14:33 ` Brent Cook
2006-04-21 21:51 ` Benjamin Herrenschmidt
2006-04-27 21:31 ` Mark A. Greer
2006-04-27 21:53 ` Benjamin Herrenschmidt
2006-04-27 22:08 ` Mark A. Greer
2006-04-29 17:57 ` Gerhard Pircher
2006-04-20 21:06 ` Benjamin Herrenschmidt
2006-04-20 21:13 ` Eugene Surovegin
2006-04-20 21:19 ` Eugene Surovegin
2006-04-20 22:40 ` Benjamin Herrenschmidt
2006-04-20 22:39 ` Benjamin Herrenschmidt
2006-04-20 23:46 ` Gabriel Paubert
2006-04-21 0:09 ` Benjamin Herrenschmidt
2006-04-20 21:33 ` Eugene Surovegin [this message]
2006-04-20 22:41 ` Benjamin Herrenschmidt
2006-04-21 8:21 ` Gerhard Pircher
2006-04-20 21:03 ` Benjamin Herrenschmidt
2006-04-20 21:33 ` Gerhard Pircher
2006-04-20 22:07 ` Gabriel Paubert
2006-04-20 22:26 ` Gerhard Pircher
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=20060420213316.GD25755@gate.ebshome.net \
--to=ebs@ebshome.net \
--cc=benh@kernel.crashing.org \
--cc=debian-powerpc@lists.debian.org \
--cc=linuxppc-dev@ozlabs.org \
/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.