[PATCH] mm: add an option to disable bounce

[PATCH] mm: add an option to disable bounce

[vinayakm.list]

From: Vinayak Menon <vinayakm.list@gmail.com>

There are times when HIGHMEM is enabled, but
we don't prefer CONFIG_BOUNCE to be enabled.
CONFIG_BOUNCE can reduce the block device
throughput, and this is not ideal for machines
where we don't gain much by enabling it. So
provide an option to deselect CONFIG_BOUNCE. The
observation was made while measuring eMMC throughput
using iozone on an ARM device with 1GB RAM.

Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
---
 mm/Kconfig |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 3bea74f..29f9736 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
 	default "1"
 
 config BOUNCE
+	bool "Enable bounce buffers"
 	def_bool y
 	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
+	help
+	  Enable bounce buffers for devices that cannot access
+	  the full range of memory available to the CPU. Enabled
+	  by default when ZONE_DMA or HIGMEM is selected, but you
+	  may say n to override this.
 
 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 # have more than 4GB of memory, but we don't currently use the IOTLB to present
-- 
1.7.10.4

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Re: [PATCH] mm: add an option to disable bounce

[Randy Dunlap]

On 04/22/13 08:23, vinayakm.list@gmail.com wrote:
> From: Vinayak Menon <vinayakm.list@gmail.com>
> 
> There are times when HIGHMEM is enabled, but
> we don't prefer CONFIG_BOUNCE to be enabled.
> CONFIG_BOUNCE can reduce the block device
> throughput, and this is not ideal for machines
> where we don't gain much by enabling it. So
> provide an option to deselect CONFIG_BOUNCE. The
> observation was made while measuring eMMC throughput
> using iozone on an ARM device with 1GB RAM.
> 
> Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
> ---
>  mm/Kconfig |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3bea74f..29f9736 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
>  	default "1"
>  
>  config BOUNCE
> +	bool "Enable bounce buffers"
>  	def_bool y
>  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
> +	help
> +	  Enable bounce buffers for devices that cannot access
> +	  the full range of memory available to the CPU. Enabled
> +	  by default when ZONE_DMA or HIGMEM is selected, but you

	                              HIGHMEM

> +	  may say n to override this.
>  
>  # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
>  # have more than 4GB of memory, but we don't currently use the IOTLB to present
> 


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~Randy

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Re: [PATCH] mm: add an option to disable bounce

[vinayak]

On Monday 22 April 2013 10:28 PM, Randy Dunlap wrote:

> On 04/22/13 08:23, vinayakm.list@gmail.com wrote:
>> From: Vinayak Menon <vinayakm.list@gmail.com>
>>
>> There are times when HIGHMEM is enabled, but
>> we don't prefer CONFIG_BOUNCE to be enabled.
>> CONFIG_BOUNCE can reduce the block device
>> throughput, and this is not ideal for machines
>> where we don't gain much by enabling it. So
>> provide an option to deselect CONFIG_BOUNCE. The
>> observation was made while measuring eMMC throughput
>> using iozone on an ARM device with 1GB RAM.
>>
>> Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
>> ---
>>  mm/Kconfig |    6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index 3bea74f..29f9736 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
>>  	default "1"
>>  
>>  config BOUNCE
>> +	bool "Enable bounce buffers"
>>  	def_bool y
>>  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
>> +	help
>> +	  Enable bounce buffers for devices that cannot access
>> +	  the full range of memory available to the CPU. Enabled
>> +	  by default when ZONE_DMA or HIGMEM is selected, but you
> 
> 	                              HIGHMEM


Thanks. I will correct this.

> 
>> +	  may say n to override this.
>>  
>>  # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
>>  # have more than 4GB of memory, but we don't currently use the IOTLB to present
>>
> 
> 


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Re: [PATCH] mm: add an option to disable bounce

[Russell King - ARM Linux]

On Mon, Apr 22, 2013 at 08:53:00PM +0530, vinayakm.list@gmail.com wrote:
> From: Vinayak Menon <vinayakm.list@gmail.com>
> 
> There are times when HIGHMEM is enabled, but
> we don't prefer CONFIG_BOUNCE to be enabled.
> CONFIG_BOUNCE can reduce the block device
> throughput, and this is not ideal for machines
> where we don't gain much by enabling it. So
> provide an option to deselect CONFIG_BOUNCE. The
> observation was made while measuring eMMC throughput
> using iozone on an ARM device with 1GB RAM.
> 
> Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
> ---
>  mm/Kconfig |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3bea74f..29f9736 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
>  	default "1"
>  
>  config BOUNCE
> +	bool "Enable bounce buffers"
>  	def_bool y
>  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)

I don't think this is correct.  You shouldn't use "bool" with "def_bool".
Sure, add the "bool", but also change "def_bool" to "default".

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Re: [PATCH] mm: add an option to disable bounce

[vinayak]

On Monday 22 April 2013 11:17 PM, Russell King - ARM Linux wrote:

> On Mon, Apr 22, 2013 at 08:53:00PM +0530, vinayakm.list@gmail.com wrote:
>> From: Vinayak Menon <vinayakm.list@gmail.com>
>>
>> There are times when HIGHMEM is enabled, but
>> we don't prefer CONFIG_BOUNCE to be enabled.
>> CONFIG_BOUNCE can reduce the block device
>> throughput, and this is not ideal for machines
>> where we don't gain much by enabling it. So
>> provide an option to deselect CONFIG_BOUNCE. The
>> observation was made while measuring eMMC throughput
>> using iozone on an ARM device with 1GB RAM.
>>
>> Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
>> ---
>>  mm/Kconfig |    6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index 3bea74f..29f9736 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
>>  	default "1"
>>  
>>  config BOUNCE
>> +	bool "Enable bounce buffers"
>>  	def_bool y
>>  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
> 
> I don't think this is correct.  You shouldn't use "bool" with "def_bool".
> Sure, add the "bool", but also change "def_bool" to "default".


Yes. I will change it to "default" and this looks to be correct
even from the definition in kconfig-language.txt. But I see other
instances in mm/Kconfig, where bool and def_bool are used together. When
I had tested this patch with def_bool, it worked as expected.

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Re: [PATCH] mm: add an option to disable bounce

[KOSAKI Motohiro]

(4/22/13 11:23 AM), vinayakm.list@gmail.com wrote:
> From: Vinayak Menon <vinayakm.list@gmail.com>
> 
> There are times when HIGHMEM is enabled, but
> we don't prefer CONFIG_BOUNCE to be enabled.
> CONFIG_BOUNCE can reduce the block device
> throughput, and this is not ideal for machines
> where we don't gain much by enabling it. So
> provide an option to deselect CONFIG_BOUNCE. The
> observation was made while measuring eMMC throughput
> using iozone on an ARM device with 1GB RAM.
> 
> Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com>
> ---
>  mm/Kconfig |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 3bea74f..29f9736 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
>  	default "1"
>  
>  config BOUNCE
> +	bool "Enable bounce buffers"
>  	def_bool y
>  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
> +	help
> +	  Enable bounce buffers for devices that cannot access
> +	  the full range of memory available to the CPU. Enabled
> +	  by default when ZONE_DMA or HIGMEM is selected, but you
> +	  may say n to override this.

This should depend on CONFIG_EXPERT. Because this makes typically worse result
on typical desktop machine.






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