linux-kernel - Re: [patch 1/1] combine two adjacent mtrr region with the same type

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Date:	Fri, 10 Oct 2008 11:59:31 +0800
From:	bmao <bmao@...are.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	bibo mao <bibo.mao@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [patch 1/1] combine two adjacent mtrr region with the same type

Yinghai Lu wrote:
> bibo mao wrote:
>> This patch is to combine two adjacent mtrr region with the same type.
>>
>>  kernel/cpu/mtrr/main.c          |   17 +++++++++++++++--
>>  3 files changed, 15 insertions(+), 2 deletions(-)
>>
>> Signed-off-by: bibo mao <bibo.mao@...il.com>
>>
>> -------------------------------------------------------------------------------
>> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
>> index 6e212f3..c3adf83 100644
>> --- a/arch/x86/kernel/cpu/mtrr/main.c
>> +++ b/arch/x86/kernel/cpu/mtrr/main.c
>> @@ -305,7 +305,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
>>  {
>>       int i, j, replace, error;
>>       mtrr_type ltype;
>> -     unsigned long lbase, lsize;
>> +     unsigned long lbase, lsize, newbase;
>>
>>       if (!mtrr_if)
>>               return -ENXIO;
>> @@ -344,7 +344,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
>>       mutex_lock(&mtrr_mutex);
>>       for (i = 0; i < num_var_ranges; ++i) {
>>               mtrr_if->get(i, &lbase, &lsize, &ltype);
>> -             if (!lsize || base > lbase + lsize - 1 || base + size - 1 < lbase)
>> +             if (!lsize || base > lbase + lsize || base + size < lbase)
>>                       continue;
>>               /*  At this point we know there is some kind of overlap/enclosure  */
>>               if (base < lbase || base + size - 1 > lbase + lsize - 1) {
>> @@ -356,6 +356,19 @@ int mtrr_add_page(unsigned long base, unsigned long size,
>>                               }
>>                               else if (types_compatible(type, ltype))
>>                                       continue;
>> +                     } else if ((base == lbase + lsize) || (lbase ==base + size)) {
>> +                             if (type != ltype)
>> +                                     continue;
> this path seems not right...
> 
> do you need
> 
>                 if (ltype != type) {
>                         if (types_compatible(type, ltype))
>                                 continue;
>                         printk (KERN_WARNING "mtrr: type mismatch for %lx000,%lx000 old: %s new: %s\n",
>                              base, size, mtrr_attrib_to_str(ltype),
>                              mtrr_attrib_to_str(type));
>                         goto out;
>                 }
> ?
This warning info is for two enclosed mtrr region, but it is adjacent here. Here is no overlapped mtrr region even.
> 
> 
> 
> 
>> +                             /* New region adjacent with an existing region  */
>> +                             newbase = (base < lbase) ? base : lbase;
>> +                             if (!mtrr_if->validate_add_page(newbase,lsize + size,type) &&
>> +                                mtrr_if->get_free_region(newbase, lsize + size, replace)>=0) {
>> +                                     base = newbase;
>> +                                     size += lsize;
>> +                                     replace = i;
>> +                                     continue;
>> +                             } else
>> +                                     continue;
>>                       }
>>                       printk(KERN_WARNING
>>                              "mtrr: 0x%lx000,0x%lx000 overlaps existing"
> 
> better to have some test case...
> 
> YH
> 
Here is test result: 

# echo "base=0x02000000 size=0x00800000 type=write-back" >| /proc/mtrr
# echo "base=0x03000000 size=0x01000000 type=write-back" >| /proc/mtrr
# cat /proc/mtrr 
reg00: base=0x02000000 (  32MB), size=   8MB: write-back, count=1
reg01: base=0x03000000 (  48MB), size=  16MB: write-back, count=1

# echo "base=0x02800000 size=0x00800000 type=write-back" >| /proc/mtrr
# cat /proc/mtrr 
reg01: base=0x02000000 (  32MB), size=  32MB: write-back, count=3

Without this patch, it will display with this result:

reg00: base=0x02000000 (  32MB), size=   8MB: write-back, count=1
reg01: base=0x03000000 (  48MB), size=  16MB: write-back, count=1
reg02: base=0x02800000 (  40MB), size=   8MB: write-back, count=1

thanks
bibo,mao
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