Patch for Definition of ref-cycles event for AMD Zen 4 and later  

Instructions for this README were developed on  OpenCloudOS 9.0. This patch defines a proper ref-cycles event for Zen 4 hosts and later. 

Please follow these instructions to build, install and verify  kernel support

1. Get the Linux source tree
- #git clone https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel
- #cd OpenCloudOS-Kernel
- #git checkout next
- #git tag; git checkout 6.6.26-1
- #Download the patches to PATCHDIR [ ex:PATCHDIR=/tmp/kernelpatch ] & apply patches in this repo:
- git apply $PATCHDIR/*.patch

2.Configure,  build the kernel and create packages
- #cp /boot/config-$(uname -r) .config 
- #yes "" | make olddefconfig
- #make -j `getconf _NPROCESSORS_ONLN` 
- #sudo make -j`getconf _NPROCESSORS_ONLN`  rpm-pkg
   
3. Install the backported package 
- #cd ..
- #sudo rpm -ivh <kernel-6.6.26_*.x86_64.rpm> (Path to patched kernel)

4. reboot and select the patched kernel

5. Install perf and perftest tool to verify patched kernel.
 - #sudo dnf install perf-6.6.6-2401.0.1.oc9.x86_64 perftest-4.5-4.oc9.x86_64 -y


6. Verify / test installed patch using perf tool on AMD Zen 4 host as follows.
 a) Without patch:
===================
     #perf list | grep ref-cycles
	(No output) 
     #perf stat -e "{ref-cycles, cpu/ref-cycles/}" sleep 5
	Error:
	The ref-cycles:u event is not supported.


 b) With patch:
===================
     #perf list | grep ref-cycles
	  ref-cycles                                         [Hardware event]
  	  ref-cycles OR cpu/ref-cycles/                      [Kernel PMU event]

     #perf stat -e "{ref-cycles, cpu/ref-cycles/}" sleep 5

      Performance counter stats for 'sleep 5':

           371,296      ref-cycles:u
           371,296       cpu/ref-cycles/u

       5.002200577 seconds time elapsed

       0.000000000 seconds user
       0.001862000 seconds sys

 Perf Counter statistics can be captured for the ref-cycles events defined by the patch, using perf stat -e command shown above.