How do I use performance counters inside of the kernel?

Question

I want to access performance counters inside the kernel. I found many ways to use performance counters in user space, but can you tell me some way to use those in kernel space.

Please don't specify tool name, I want to write my own code, preferably a kernel module. I am using Ubuntu with kernel 3.18.1.

score 2 · Answer 1 · answered Apr 27 '15 at 12:57

2

http://www.cise.ufl.edu/~sb3/files/pmc.pdf http://www.cs.inf.ethz.ch/stricker/lab/doc/intel-part4.pdf The first pdf contains description on how to use pmc.

The second contains the address of perfeventsel0 and perfeventsel1. Ive shown an example below.U'll need to set the event number and umask as per ur requirement.

void SetUpEvent(void){
int reg_addr=0x186; 
int event_no=0x0024; 
int umask=0x3F00; 
int enable_bits=0x430000; 
int event=event_no | umask | enable_bits;


__asm__ ("wrmsr" : : "c"(reg_addr), "a"(event), "d"(0x00));

}

/* Read the performance monitor counter */
long int ReadCounter(void){
    long int count;
    long int eax_low, edx_high;
    int reg_addr=0xC1; 


    __asm__("rdmsr" : "=a"(eax_low), "=d"(edx_high) : "c"(reg_addr));
    count = ((long int)eax_low | (long int)edx_high<<32);

    return count;
}

answered Apr 27 '15 at 12:57

njn1234

341
2
5

Why are you using only perfeveset0 register and not perfctr0 ? Or where and how we will use these two ? Moreover can you write a full working example because it will be helpful for the people who will search for it later. – A-B Apr 28 '15 at 05:35
u can use this in a kernel module or directly modifying the linux kernel. – njn1234 May 05 '15 at 07:48
0xc1 is the perfctr0 we set an event using perfeventsel0 and read ctr value from perfctr0. – njn1234 May 05 '15 at 10:50

score 1 · Answer 2 · answered Apr 22 '15 at 15:18

You should check if you CPU and other HW support you needs. Try look into oprofile source code. It have kernel module and userspace api. You can for example cut part of interesting code from oprofile kernel module part and use it into you module. I gues you module should have several reader or listeners with circle buffers for events keeping. You can also look inside linux/drivers/oprofile and to correspond linux/arch/.../oprofile. Inside make menuconfig you can config it like module or build-in and add additional timers. Available events and counters you can find under oprofile/events/ of oprofile tool (TLB_MISS, CPU_CYCLES, CYCLES_DATA_STALL, ...).

ARM Performance monitoring register

Under linux/arch/arm64/kernel/perf_regs.c you can find arm specific details.

How do I use performance counters inside of the kernel?

2 Answers2

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