Using perf on AMD 15h

Using perf on AMD 15h

[Mahmood Naderan]

Hi Guys,
My first question is, does the version of kernel affects the perf
functionality? I mean fixing bugs and ...
Currently, the kernel version is 2.6.39 and here is the problem:

According tot he BKDG of AMD 15h, it is possbile to disable the
hardware prefetcher by setting some bits of MSRC001_1022

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.



So in order to disable all prefetch configs, I have to write 0xA008 to
that MSR. I did that for all cores using

[root@tiger exe]# wrmsr -a 0xc0011022 0xA008
[root@tiger exe]# rdmsr -a -x -0 0xc0011022
000000000000a008
...


However, when I run perf along with the command, the prefetch ststs
are non-zero!


[root@tiger exe]# perf stat -e
L1-dcache-loads:uk,L1-dcache-prefetches:uk,L1-dcache-prefetch-misses:uk
./bzip2_base.amd64-m64-gcc44-nn
spec_init
Tested 64MB buffer: OK!
 Performance counter stats for './bzip2_base.amd64-m64-gcc44-nn':
    55,341,597,193 L1-dcache-loads:uk
     1,047,662,614 L1-dcache-prefetches:uk
                 0 L1-dcache-prefetch-misses:uk
      35.921618464 seconds time elapsed




I expect to see 0 in front of  L1-dcache-prefetches. Don't you?
I have stuck at this problem. I appreciate any feedback and comment.


Regards,
Mahmood

Re: Using perf on AMD 15h

[Mahmood Naderan]

Bringing up my question one more time since it may be lost in the high
volume of messages.

Hope to receive an idea...



On 6/6/15, Mahmood Naderan <mahmood.nt@gmail.com> wrote:
> Hi Guys,
> My first question is, does the version of kernel affects the perf
> functionality? I mean fixing bugs and ...
> Currently, the kernel version is 2.6.39 and here is the problem:
>
> According tot he BKDG of AMD 15h, it is possbile to disable the
> hardware prefetcher by setting some bits of MSRC001_1022
>
> 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.
>
>
>
> So in order to disable all prefetch configs, I have to write 0xA008 to
> that MSR. I did that for all cores using
>
> [root@tiger exe]# wrmsr -a 0xc0011022 0xA008
> [root@tiger exe]# rdmsr -a -x -0 0xc0011022
> 000000000000a008
> ...
>
>
> However, when I run perf along with the command, the prefetch ststs
> are non-zero!
>
>
> [root@tiger exe]# perf stat -e
> L1-dcache-loads:uk,L1-dcache-prefetches:uk,L1-dcache-prefetch-misses:uk
> ./bzip2_base.amd64-m64-gcc44-nn
> spec_init
> Tested 64MB buffer: OK!
>  Performance counter stats for './bzip2_base.amd64-m64-gcc44-nn':
>     55,341,597,193 L1-dcache-loads:uk
>      1,047,662,614 L1-dcache-prefetches:uk
>                  0 L1-dcache-prefetch-misses:uk
>       35.921618464 seconds time elapsed
>
>
>
>
> I expect to see 0 in front of  L1-dcache-prefetches. Don't you?
> I have stuck at this problem. I appreciate any feedback and comment.
>
>
> Regards,
> Mahmood
>


-- 
Regards,
Mahmood