From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@lst.de>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
David Airlie <airlied@linux.ie>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
Intel Linux Wireless <linuxwifi@intel.com>,
"intel-gfx@lists.freedesktop.org"
<intel-gfx@lists.freedesktop.org>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Ian Abbott <abbotti@mev.co.uk>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Sean Paul <sean@poorly.run>,
"moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
H Hartley Sweeten <hsweeten@visionengravers.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Daniel Vetter <daniel@ffwll.ch>
Subject: RE: [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous
Date: Fri, 14 Jun 2019 15:01:22 +0000 [thread overview]
Message-ID: <d93fd4c2c1584d92a05dd641929f6d63@AcuMS.aculab.com> (raw)
In-Reply-To: <20190614145001.GB9088@lst.de>
From: 'Christoph Hellwig'
> Sent: 14 June 2019 15:50
> To: David Laight
> On Fri, Jun 14, 2019 at 02:15:44PM +0000, David Laight wrote:
> > Does this still guarantee that requests for 16k will not cross a 16k boundary?
> > It looks like you are losing the alignment parameter.
>
> The DMA API never gave you alignment guarantees to start with,
> and you can get not naturally aligned memory from many of our
> current implementations.
Hmmm...
I thought that was even documented.
I'm pretty sure there is a lot of code out there that makes that assumption.
Without it many drivers will have to allocate almost double the
amount of memory they actually need in order to get the required alignment.
So instead of saving memory you'll actually make more be used.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2019-06-14 15:01 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-14 13:47 use exact allocation for dma coherent memory Christoph Hellwig
2019-06-14 13:47 ` [PATCH 01/16] media: videobuf-dma-contig: use dma_mmap_coherent Christoph Hellwig
2019-06-14 13:47 ` [PATCH 02/16] drm/ati_pcigart: stop using drm_pci_alloc Christoph Hellwig
2019-06-14 13:47 ` [PATCH 03/16] drm/i915: " Christoph Hellwig
2019-06-14 16:45 ` [Intel-gfx] " Ville Syrjälä
2019-06-14 13:47 ` [PATCH 04/16] drm: move drm_pci_{alloc,free} to drm_legacy Christoph Hellwig
2019-06-14 13:47 ` [PATCH 05/16] drm: don't mark pages returned from drm_pci_alloc reserved Christoph Hellwig
2019-06-14 13:47 ` [PATCH 06/16] drm: don't pass __GFP_COMP to dma_alloc_coherent in drm_pci_alloc Christoph Hellwig
2019-06-14 13:47 ` [PATCH 07/16] IB/hfi1: stop passing bogus gfp flags arguments to dma_alloc_coherent Christoph Hellwig
2019-06-14 13:47 ` [PATCH 08/16] IB/qib: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 09/16] cnic: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 10/16] iwlwifi: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 11/16] s390/ism: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 12/16] staging/comedi: mark as broken Christoph Hellwig
2019-06-14 14:02 ` Greg KH
2019-06-14 14:48 ` Christoph Hellwig
2019-06-14 15:30 ` Greg KH
2019-06-14 15:34 ` Christoph Hellwig
2019-06-17 13:15 ` Ian Abbott
2019-06-14 13:47 ` [PATCH 13/16] mm: rename alloc_pages_exact_nid to alloc_pages_exact_node Christoph Hellwig
2019-06-14 13:47 ` [PATCH 14/16] mm: use alloc_pages_exact_node to implement alloc_pages_exact Christoph Hellwig
2019-06-14 13:47 ` [PATCH 15/16] dma-mapping: clear __GFP_COMP in dma_alloc_attrs Christoph Hellwig
2019-06-14 13:47 ` [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous Christoph Hellwig
2019-06-14 14:15 ` David Laight
2019-06-14 14:50 ` 'Christoph Hellwig'
2019-06-14 15:01 ` David Laight [this message]
2019-06-14 15:05 ` 'Christoph Hellwig'
2019-06-14 15:05 ` Robin Murphy
2019-06-14 15:08 ` 'Christoph Hellwig'
2019-06-14 15:16 ` David Laight
2019-06-17 8:21 ` use exact allocation for dma coherent memory Dan Carpenter
2019-06-17 8:33 ` Christoph Hellwig
2019-06-19 16:29 ` Jason Gunthorpe
2019-06-20 10:51 ` Christoph Hellwig
2019-07-01 8:48 ` Christoph Hellwig
2019-07-02 9:48 ` Arend Van Spriel via iommu
2019-07-08 18:43 ` Christoph Hellwig
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=d93fd4c2c1584d92a05dd641929f6d63@AcuMS.aculab.com \
--to=david.laight@aculab.com \
--cc=abbotti@mev.co.uk \
--cc=airlied@linux.ie \
--cc=daniel@ffwll.ch \
--cc=devel@driverdev.osuosl.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@lst.de \
--cc=hsweeten@visionengravers.com \
--cc=intel-gfx@lists.freedesktop.org \
--cc=iommu@lists.linux-foundation.org \
--cc=jani.nikula@linux.intel.com \
--cc=joonas.lahtinen@linux.intel.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux-wireless@vger.kernel.org \
--cc=linuxwifi@intel.com \
--cc=maarten.lankhorst@linux.intel.com \
--cc=maxime.ripard@bootlin.com \
--cc=netdev@vger.kernel.org \
--cc=rodrigo.vivi@intel.com \
--cc=sean@poorly.run \
/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;
as well as URLs for NNTP newsgroup(s).