]> git.baikalelectronics.ru Git - kernel.git/commit
powerpc/mm: don't do tlbie for updatepp request with NO HPTE fault
authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Thu, 4 Dec 2014 05:30:14 +0000 (11:00 +0530)
committerMichael Ellerman <mpe@ellerman.id.au>
Fri, 5 Dec 2014 05:26:15 +0000 (16:26 +1100)
commite23e847100142238a0e3cc0aa508bf9b8ddab38f
treed6036007b0eca0b325aa3f050defb00f89341209
parentdbf4d6f0cf0181c78b2384fbfe256dad66cca54f
powerpc/mm: don't do tlbie for updatepp request with NO HPTE fault

upatepp can get called for a nohpte fault when we find from the linux
page table that the translation was hashed before. In that case
we are sure that there is no existing translation, hence we could
avoid doing tlbie.

We could possibly race with a parallel fault filling the TLB. But
that should be ok because updatepp is only ever relaxing permissions.
We also look at linux pte permission bits when filling hash pte
permission bits. We also hold the linux pte busy bits while
inserting/updating a hashpte entry, hence a paralle update of
linux pte is not possible. On the other hand mprotect involves
ptep_modify_prot_start which cause a hpte invalidate and not updatepp.

Performance number:
We use randbox_access_bench written by Anton.

Kernel with THP disabled and smaller hash page table size.

    86.60%  random_access_b  [kernel.kallsyms]                [k] .native_hpte_updatepp
     2.10%  random_access_b  random_access_bench              [.] doit
     1.99%  random_access_b  [kernel.kallsyms]                [k] .do_raw_spin_lock
     1.85%  random_access_b  [kernel.kallsyms]                [k] .native_hpte_insert
     1.26%  random_access_b  [kernel.kallsyms]                [k] .native_flush_hash_range
     1.18%  random_access_b  [kernel.kallsyms]                [k] .__delay
     0.69%  random_access_b  [kernel.kallsyms]                [k] .native_hpte_remove
     0.37%  random_access_b  [kernel.kallsyms]                [k] .clear_user_page
     0.34%  random_access_b  [kernel.kallsyms]                [k] .__hash_page_64K
     0.32%  random_access_b  [kernel.kallsyms]                [k] fast_exception_return
     0.30%  random_access_b  [kernel.kallsyms]                [k] .hash_page_mm

With Fix:

    27.54%  random_access_b  random_access_bench              [.] doit
    22.90%  random_access_b  [kernel.kallsyms]                [k] .native_hpte_insert
     5.76%  random_access_b  [kernel.kallsyms]                [k] .native_hpte_remove
     5.20%  random_access_b  [kernel.kallsyms]                [k] fast_exception_return
     5.12%  random_access_b  [kernel.kallsyms]                [k] .__hash_page_64K
     4.80%  random_access_b  [kernel.kallsyms]                [k] .hash_page_mm
     3.31%  random_access_b  [kernel.kallsyms]                [k] data_access_common
     1.84%  random_access_b  [kernel.kallsyms]                [k] .trace_hardirqs_on_caller

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
16 files changed:
arch/powerpc/include/asm/machdep.h
arch/powerpc/include/asm/mmu-hash64.h
arch/powerpc/include/asm/tlbflush.h
arch/powerpc/kernel/exceptions-64s.S
arch/powerpc/mm/hash_low_64.S
arch/powerpc/mm/hash_native_64.c
arch/powerpc/mm/hash_utils_64.c
arch/powerpc/mm/hugepage-hash64.c
arch/powerpc/mm/hugetlbpage-hash64.c
arch/powerpc/mm/pgtable_64.c
arch/powerpc/platforms/cell/beat_htab.c
arch/powerpc/platforms/cell/spu_base.c
arch/powerpc/platforms/cell/spufs/fault.c
arch/powerpc/platforms/ps3/htab.c
arch/powerpc/platforms/pseries/lpar.c
drivers/misc/cxl/fault.c