From: Dan Williams <dan.j.williams@intel.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Jens Axboe <axboe@kernel.dk>, Michal Simek <monstr@monstr.eu>,
Russell King <linux@arm.linux.org.uk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Julia Lawall <Julia.Lawall@lip6.fr>,
"dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
David Woodhouse <dwmw2@infradead.org>,
Christoph Hellwig <hch@lst.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] scatterlist: use sg_phys()
Date: Wed, 10 Jun 2015 09:00:31 -0700 [thread overview]
Message-ID: <CAPcyv4gat8TG9YnHmvD_7A7RD00Urn=febCj2Uc_cVcPi+fnCg@mail.gmail.com> (raw)
In-Reply-To: <20150610093252.GA20384@8bytes.org>
On Wed, Jun 10, 2015 at 2:32 AM, Joerg Roedel <joro@8bytes.org> wrote:
> On Tue, Jun 09, 2015 at 12:27:10PM -0400, Dan Williams wrote:
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index 7e7583ddd607..9f6ff6671f01 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -1502,7 +1502,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
>> return -ENOMEM;
>>
>> for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) {
>> - phys_addr_t phys = page_to_phys(sg_page(s));
>> + phys_addr_t phys = sg_phys(s) - s->offset;
>
> So sg_phys() turns out to be 'page_to_phys(sg_page(s)) + s->offset',
> which makes the above statement to:
>
> page_to_phys(sg_page(s)) + s->offset - s->offset;
>
> The compiler will probably optimize that away, but it still doesn't look
> like an improvement.
The goal is to eventually stop leaking struct page deep into the i/o
stack. Anything that relies on being able to retrieve a struct page
out of an sg entry needs to be converted. I think we need a new
helper for this case "sg_phys_aligned()?".
WARNING: multiple messages have this Message-ID (diff)
From: dan.j.williams@intel.com (Dan Williams)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] scatterlist: use sg_phys()
Date: Wed, 10 Jun 2015 09:00:31 -0700 [thread overview]
Message-ID: <CAPcyv4gat8TG9YnHmvD_7A7RD00Urn=febCj2Uc_cVcPi+fnCg@mail.gmail.com> (raw)
In-Reply-To: <20150610093252.GA20384@8bytes.org>
On Wed, Jun 10, 2015 at 2:32 AM, Joerg Roedel <joro@8bytes.org> wrote:
> On Tue, Jun 09, 2015 at 12:27:10PM -0400, Dan Williams wrote:
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index 7e7583ddd607..9f6ff6671f01 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -1502,7 +1502,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
>> return -ENOMEM;
>>
>> for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) {
>> - phys_addr_t phys = page_to_phys(sg_page(s));
>> + phys_addr_t phys = sg_phys(s) - s->offset;
>
> So sg_phys() turns out to be 'page_to_phys(sg_page(s)) + s->offset',
> which makes the above statement to:
>
> page_to_phys(sg_page(s)) + s->offset - s->offset;
>
> The compiler will probably optimize that away, but it still doesn't look
> like an improvement.
The goal is to eventually stop leaking struct page deep into the i/o
stack. Anything that relies on being able to retrieve a struct page
out of an sg entry needs to be converted. I think we need a new
helper for this case "sg_phys_aligned()?".
next prev parent reply other threads:[~2015-06-10 16:00 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 16:27 [PATCH 0/2] scatterlist cleanups Dan Williams
2015-06-09 16:27 ` Dan Williams
2015-06-09 16:27 ` [PATCH 1/2] scatterlist: use sg_phys() Dan Williams
2015-06-09 16:27 ` Dan Williams
2015-06-10 0:34 ` Elliott, Robert (Server Storage)
2015-06-10 0:34 ` Elliott, Robert (Server Storage)
2015-06-10 9:32 ` Joerg Roedel
2015-06-10 9:32 ` Joerg Roedel
2015-06-10 16:00 ` Dan Williams [this message]
2015-06-10 16:00 ` Dan Williams
2015-06-10 16:31 ` Russell King - ARM Linux
2015-06-10 16:31 ` Russell King - ARM Linux
2015-06-10 16:57 ` Dan Williams
2015-06-10 16:57 ` Dan Williams
2015-06-10 17:13 ` Russell King - ARM Linux
2015-06-10 17:13 ` Russell King - ARM Linux
2015-06-10 17:25 ` Dan Williams
2015-06-10 17:25 ` Dan Williams
2015-06-11 6:50 ` Joerg Roedel
2015-06-11 6:50 ` Joerg Roedel
2015-06-09 16:27 ` [PATCH 2/2] scatterlist: cleanup sg_chain() and sg_unmark_end() Dan Williams
2015-06-09 16:27 ` Dan Williams
2015-06-10 5:38 ` Herbert Xu
2015-06-10 5:38 ` Herbert Xu
2015-06-11 7:31 ` Christoph Hellwig
2015-06-11 7:31 ` Christoph Hellwig
2015-06-11 7:34 ` Herbert Xu
2015-06-11 7:34 ` Herbert Xu
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