Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: > On Mon, 2015-09-21 at 12:10 +0530, Aneesh Kumar K.V wrote: >> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> >> --- >> arch/powerpc/mm/Makefile | 3 + >> arch/powerpc/mm/hash64_64k.c | 204 +++++++++++++++++++++ >> arch/powerpc/mm/hash_low_64.S | 380 ------------------------------ >> ---------- >> arch/powerpc/mm/hash_utils_64.c | 4 +- >> 4 files changed, 210 insertions(+), 381 deletions(-) >> create mode 100644 arch/powerpc/mm/hash64_64k.c > > Did you check if there was any measurable performance difference ? >
I looked at the performance number with and without patch. I don't see much impact in the numbers. We do have a path lengh increase ( I measured this using systemsim) Path length __hash_page_4k with patch: 196 without patch: 142 Path length __hash_page_64k with patch: 219 without patch: 154 But even if we have a path lengh increase of around 50 instructions. We don't see the impact when running workload. I tried the kernelbuild test. With THP enabled (which is default) we see an improvement. I haven't fully looked at the reason. This could be due to reduced contention of ptl lock. __hash_thp_page is already a C code. make -j64 vmlinux modules With fix: --------- real 1m35.509s user 56m8.565s sys 4m34.973s real 1m32.174s user 57m2.336s sys 4m39.142s Without fix: --------------- real 1m37.703s user 58m50.783s sys 7m52.440s real 1m37.890s user 57m55.445s sys 7m50.501s THP disabled: make -j64 vmlinux modules With fix: --------- real 1m37.197s user 58m28.672s sys 7m58.188s real 1m44.638s user 58m37.551s sys 7m53.960s Without fix: ------------ real 1m41.224s user 58m46.944s sys 7m49.714s real 1m42.585s user 59m14.019s sys 7m52.714s -aneesh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
