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From: Robin Murphy <robin.murphy@arm.com>
To: Christoph Hellwig <hch@infradead.org>,
	Nicolin Chen <nicoleotsuka@gmail.com>
Cc: joro@8bytes.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist
Date: Tue, 6 Nov 2018 14:39:26 +0000	[thread overview]
Message-ID: <afdc0e33-db18-6ad9-61cd-919fe3df1b4e@arm.com> (raw)
In-Reply-To: <20181105145847.GA31337@infradead.org>

On 05/11/2018 14:58, Christoph Hellwig wrote:
> On Fri, Nov 02, 2018 at 04:36:13PM -0700, Nicolin Chen wrote:
>>> What if the pages came from highmem? I know that doesn't happen on arm64
>>> today, but the point of this code *is* to be generic, and other users will
>>> arrive eventually.
>>
>> Hmm, so it probably should use sg_miter_start/stop() too? Looking
>> at the flush routine doing in PAGE_SIZE for each iteration, would
>> be possible to map and memset contiguous pages together? Actually
>> the flush routine might be also optimized if we can map contiguous
>> pages.
> 
> FYI, I have patches I plan to submit soon that gets rid of the
> struct scatterlist use in this code to simplify it:

...and I have some significant objections to that simplification which I 
plan to respond with ;)

(namely that it defaults the whole higher-order page allocation business 
which will have varying degrees of performance impact on certain cases)

Robin.

  reply	other threads:[~2018-11-06 14:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 21:35 [PATCH] iommu/dma: Zero pages manually in a length of scatterlist Nicolin Chen
2018-11-02 16:54 ` Robin Murphy
2018-11-02 23:36   ` Nicolin Chen
2018-11-05 14:58     ` Christoph Hellwig
2018-11-06 14:39       ` Robin Murphy [this message]
2018-11-09  7:45         ` Christoph Hellwig
2018-11-06 18:27     ` Robin Murphy
2018-11-07  0:11       ` Nicolin Chen
2018-11-04 15:50 ` Christoph Hellwig
2018-11-06 23:46   ` Nicolin Chen

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