> On Aug 20, 2019, at 7:18 AM, Dave Hansen <dave.han...@intel.com> 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
