From: Nicolas Pitre <nico@cam.org>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org,
Russell King - ARM Linux <linux@arm.linux.org.uk>
Subject: Re: [RFC] atomic highmem kmap page pinning
Date: Wed, 04 Mar 2009 21:37:43 -0500 (EST) [thread overview]
Message-ID: <alpine.LFD.2.00.0903042129140.5511@xanadu.home> (raw)
In-Reply-To: <20090305080717.f7832c63.minchan.kim@barrios-desktop>
On Thu, 5 Mar 2009, Minchan Kim wrote:
> I thought kmap and dma_map_page usage was following.
>
> kmap(page);
> ...
> dma_map_page(...)
> invalidate_cache_line
>
> kunmap(page);
>
> In this case, how do pkmap_count value for the page passed to dma_map_page become 1 ?
> The caller have to make sure to complete dma_map_page before kunmap.
The caller doesn't have to call kmap() on pages it intends to use for
DMA.
> Do I miss something ?
See above.
> > > As far as I understand, To make irq_disable to prevent this problem is
> > > rather big cost.
> >
> > How big? Could you please elaborate on the significance of this cost?
>
> I don't have a number. It depends on you for submitting this patch.
My assertion is that the cost is negligible. This is why I'm asking you
why you think this is a big cost.
Nicolas
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2009-03-05 2:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-04 5:58 Nicolas Pitre
2009-03-04 7:39 ` Andrew Morton
2009-03-04 8:14 ` Minchan Kim
2009-03-04 17:26 ` Nicolas Pitre
2009-03-04 23:07 ` Minchan Kim
2009-03-04 23:46 ` Russell King - ARM Linux
2009-03-05 0:25 ` Minchan Kim
2009-03-05 0:30 ` Minchan Kim
2009-03-05 2:37 ` Nicolas Pitre [this message]
2009-03-05 4:20 ` Minchan Kim
2009-03-05 4:57 ` Nicolas Pitre
2009-03-05 22:23 ` Minchan Kim
2009-03-05 22:59 ` Russell King - ARM Linux
2009-03-05 23:14 ` Minchan Kim
2009-03-07 22:28 ` Nicolas Pitre
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=alpine.LFD.2.00.0903042129140.5511@xanadu.home \
--to=nico@cam.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux@arm.linux.org.uk \
--cc=minchan.kim@gmail.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox