On 09/08/2018 06:38 PM, owner-linux-mm@xxxxxxxxx wrote: > > At last, here is the test result on my 4G virtual machine. I added printk > before and after sparse_memory_present_with_active_regions() and tested three > times with/without "likely". > > without with > Elapsed 0.000252 0.000250 -0.8% > > The benefit seems to be too small on a 4G virtual machine or even this is not > stable. Not sure we can see some visible effect on a 32G machine. I think it's highly unlikely you have found something significant here. It's one system, in a VM and it's not being measured using a mechanism that is suitable for benchmarking (the kernel dmesg timestamps). Plus, if this is a really tight loop, the cpu's branch predictors will be good at it.
