Am 17.07.24 um 09:52 schrieb Janosch Frank:
On 7/9/24 07:11, kernel test robot wrote:Hello, kernel test robot noticed a -34.3% regression of vm-scalability.throughput on: commit: 875fa64577da9bc8e9963ee14fef8433f20653e7 ("mm/hugetlb_vmemmap: fix race with speculative PFN walkers") https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master [still regression on linux-next/master 0b58e108042b0ed28a71cd7edf5175999955b233]This has hit s390 huge page backed KVM guests as well. Our simple start/stop test case went from ~5 to over 50 seconds of runtime.
Could this be one of the synchronize_rcu calls? This patch adds lots of them. On s390 with HZ=100 those are really expensive.
