Re: Enable/disable hardware prefetcher via Oprofile

On 06/04/2015 03:06 PM, Mahmood N wrote:
> Well I want to set/reset 13th and 15th bit number which controls the hardware prefetcher according to the BKDG
>  
> The value of 0x1000 equals 4096 which says the 13th bit is 1 and all others are zero. Here are some more examples
> 
> [root@tiger msr-tools-master]# ./wrmsr -p 0 0xc0011022 0x0
> [root@tiger msr-tools-master]# ./rdmsr -p 0 -x -0 0xc0011022
> 0000000000000000
> [root@tiger msr-tools-master]# ./wrmsr -p 0 0xc0011022 0xa
> [root@tiger msr-tools-master]# ./rdmsr -p 0 -x -0 0xc0011022
> 000000000000000a
> [root@tiger msr-tools-master]# ./wrmsr -p 0 0xc0011022 0xaa
> [root@tiger msr-tools-master]# ./rdmsr -p 0 -x -0 0xc0011022
> 000000000000000a
> [root@tiger msr-tools-master]# ./wrmsr -p 0 0xc0011022 0x3
> [root@tiger msr-tools-master]# ./rdmsr -p 0 -x -0 0xc0011022
> 0000000000000003
> [root@tiger msr-tools-master]# ./wrmsr -p 0 0xc0011022 0x1000
> [root@tiger msr-tools-master]# ./rdmsr -p 0 -x -0 0xc0011022
> 0000000000000000
> 
> 
> The last one is what I want. However, it doesn't work correctly., Surprisingly, bits 3-0 are reserved but writing 3 which is 11 correctly works!
> 

Hi,

The numbers look a bit off.

2^13 is 8192 that would be 0x2000
2^15 is 32668 that woudl be 0x8000

-Will

> 
> 
> 
> *MSRC001_1022 Data Cache Configuration (DC_CFG)*
> Bits       ///////     Description
> 63:16   ///////  Reserved.
> 15 *  ///////  DisPfHwForSw*. Read-write. Reset: 0. 1=Disable hardware prefetches for software prefetches.
> 14   ///////  Reserved.
> 13 *  ///////  DisHwPf*. Read-write. Reset: 0. 1=Disable the DC hardware prefetcher. BIOS: See 2.3.3 [Using L2 Cache as General Storage During Boot].
> 12:10   ///////  Reserved.
> 9:5   ///////  Reserved.
> 4 *  ///////  DisSpecTlbRld*. Read-write. Reset: 0. 1=Disable speculative TLB reloads. BIOS: See 2.3.3 [UsingL2 Cache as General Storage During Boot].
> 3:0   ///////  Reserved.
> 
> 
> Regards,
> Mahmood
> 
> 
> 
> 



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