I have been searching everywhere to fix this problem and tried multiple solutions to no avail. Initially it was caused by kernel_task process, which I attempted to look for any 3rd party kernel extensions, there were none. I also tried to remove the plist file from the ACPI_SMC_PlatformPlugin.kext, but I couldn't find the model macbookpro9,2 there. It went up to Macbookpro 8,3 only. I tried doing SMC reset twice, and reformatted the macbook, so it's an entirely fresh copy but the problem still persists, except the kernel_task doesn't appear on the activity monitor anymore. Extra information, safe mode is equally as slow, if not slower, and there's always a long loading bar before the mac starts. It's running on OS X Yosemite, 10.10.5. I'm beginning to think it's a hardware issue. I'm about to get professional help from Apple , this is my last resort before I do so. Any thoughts would be much appreciated.