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

[Aneesh Kumar K.V]

"Aneesh Kumar K.V" <aneesh.kumar at linux.vnet.ibm.com> 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