linux-kernel - Re: [PATCH 3/3] zsmalloc: add page table mapping method

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Date:	Sun, 22 Jul 2012 22:15:40 -0400
From:	Nitin Gupta <ngupta@...are.org>
To:	Minchan Kim <minchan@...nel.org>
CC:	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] zsmalloc: add page table mapping method

On 07/22/2012 08:26 PM, Minchan Kim wrote:
> On Wed, Jul 18, 2012 at 11:55:56AM -0500, Seth Jennings wrote:
>> This patchset provides page mapping via the page table.
>> On some archs, most notably ARM, this method has been
>> demonstrated to be faster than copying.
>>
>> The logic controlling the method selection (copy vs page table)
>> is controlled by the definition of USE_PGTABLE_MAPPING which
>> is/can be defined for any arch that performs better with page
>> table mapping.
>>
>> Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
>> ---
>>  drivers/staging/zsmalloc/zsmalloc-main.c |  182 ++++++++++++++++++++++--------
>>  drivers/staging/zsmalloc/zsmalloc_int.h  |    6 -
>>  2 files changed, 134 insertions(+), 54 deletions(-)
>>
>> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
>> index b86133f..defe350 100644
>> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
>> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
>> @@ -89,6 +89,30 @@
>>  #define CLASS_IDX_MASK	((1 << CLASS_IDX_BITS) - 1)
>>  #define FULLNESS_MASK	((1 << FULLNESS_BITS) - 1)
>>  
>> +/*
>> + * By default, zsmalloc uses a copy-based object mapping method to access
>> + * allocations that span two pages. However, if a particular architecture
>> + * 1) Implements local_flush_tlb_kernel_range() and 2) Performs VM mapping
>> + * faster than copying, then it should be added here so that
> 
> How about adding your benchmark url?
> 
>> + * USE_PGTABLE_MAPPING is defined. This causes zsmalloc to use page table
>> + * mapping rather than copying
>> + * for object mapping.
> 
> unnecessary new line.
> 
>> +*/
>> +#if defined(CONFIG_ARM)
>> +#define USE_PGTABLE_MAPPING
>> +#endif
> 
> I had no better idea and I would like to add zsmalloc into mainline.
> So no objection.
> Nitin?
> 

Same here. I just cannot think of anything better for now.

Thanks for your efforts.
Nitin


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