buffer_find_nonzero_offset() is a hot function during live migration. Now it use SSE2 intructions for optimization. For platform supports AVX2 instructions, use the AVX2 instructions for optimization can help to improve the performance about 30% comparing to SSE2. Zero page check can be faster with this optimization, the test result shows that for an 8GB RAM idle guest, this patch can help to shorten the total live migration time about 6%.
This patch use the ifunc mechanism to select the proper function when running, for platform supports AVX2, excute the AVX2 instructions, else, excute the original code. With patch, if build QEMU binary with AVX2 enabled, the binary can run on both platforms support AVX2 or not. If build QEMU binary with AVX2 diabled, or if compiler can not support AVX2, the binary will not contain the AVX2 instruction, and it can run on both platforms support AVX2 or not. Liang Li (2): cutils: add avx2 instruction optimization configure: add options to config avx2 configure | 29 ++++++++++++++++++++++ include/qemu-common.h | 28 +++++++++++++++------ util/Makefile.objs | 2 ++ util/avx2.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++ util/cutils.c | 53 +++++++++++++++++++++++++++++++++++++-- 5 files changed, 172 insertions(+), 9 deletions(-) create mode 100644 util/avx2.c -- 1.9.1
