Re: [PATCH 00/16] Remove hash page table slot tracking from linux PTE

"Aneesh Kumar K.V" [off-list ref] writes:

I looked at the perf data and with the test, we are doing larger number
of hash faults and then around 10k flush_hash_range. Can the small
improvement in number be due to the fact that we are not storing slot
number when doing an insert now?. Also in the flush path we are now not
using real_pte_t.

With THP disabled I am finding below.

Without patch

    35.62%  a.out    [kernel.vmlinux]            [k] clear_user_page
     8.54%  a.out    [kernel.vmlinux]            [k] __lock_acquire
     3.86%  a.out    [kernel.vmlinux]            [k] native_flush_hash_range
     3.38%  a.out    [kernel.vmlinux]            [k] save_context_stack
     2.98%  a.out    a.out                       [.] main
     2.59%  a.out    [kernel.vmlinux]            [k] lock_acquire
     2.29%  a.out    [kernel.vmlinux]            [k] mark_lock
     2.23%  a.out    [kernel.vmlinux]            [k] native_hpte_insert
     1.87%  a.out    [kernel.vmlinux]            [k] get_mem_cgroup_from_mm
     1.71%  a.out    [kernel.vmlinux]            [k] rcu_lockdep_current_cpu_online
     1.68%  a.out    [kernel.vmlinux]            [k] lock_release
     1.47%  a.out    [kernel.vmlinux]            [k] __handle_mm_fault
     1.41%  a.out    [kernel.vmlinux]            [k] validate_sp


With patch
    35.40%  a.out    [kernel.vmlinux]            [k] clear_user_page
     8.82%  a.out    [kernel.vmlinux]            [k] __lock_acquire
     3.66%  a.out    a.out                       [.] main
     3.49%  a.out    [kernel.vmlinux]            [k] save_context_stack
     2.77%  a.out    [kernel.vmlinux]            [k] lock_acquire
     2.45%  a.out    [kernel.vmlinux]            [k] mark_lock
     1.80%  a.out    [kernel.vmlinux]            [k] get_mem_cgroup_from_mm
     1.80%  a.out    [kernel.vmlinux]            [k] native_hpte_insert
     1.79%  a.out    [kernel.vmlinux]            [k] rcu_lockdep_current_cpu_online
     1.78%  a.out    [kernel.vmlinux]            [k] lock_release
     1.73%  a.out    [kernel.vmlinux]            [k] native_flush_hash_range
     1.53%  a.out    [kernel.vmlinux]            [k] __handle_mm_fault

That is we are now spending less time in native_flush_hash_range.

-aneesh