> On Aug 20, 2019, at 7:18 AM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > On 8/20/19 7:14 AM, Song Liu wrote: >>> *But*, that shouldn't get hit on a Skylake CPU since those have PCIDs >>> and shouldn't have a global kernel image. Could you confirm whether >>> PCIDs are supported on this CPU? >> Yes, pcid is listed in /proc/cpuinfo. > > So what's going on? Could you confirm exactly which pti_clone_pgtable() > is causing you problems? Do you have a theory as to why this manifests > as a performance problem rather than a functional one? > > A diff of these: > > /sys/kernel/debug/page_tables/current_user > /sys/kernel/debug/page_tables/current_kernel > > before and after your patch might be helpful. I believe the difference is from the following entries (7 PMDs) Before the patch: current_kernel: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte efi: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte kernel: 0xffffffff81000000-0xffffffff81e04000 14352K ro GLB x pte After the patch: current_kernel: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd efi: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd kernel: 0xffffffff81000000-0xffffffff81e00000 14M ro PSE GLB x pmd current_kernel and kernel show same data though. Thanks, Song
