why no effect after enable neon

edit

I download the opencv sourcecode 2.4.6 for android develop, after set -DANDROID_ABI="armeabi-v7a with NEON" in cmake_android_arm.sh, and I found :

ANDROID_CXX_FLAGS:INTERNAL=-Wno-psabi --sysroot=/home/sun/workspace/Kaiser/android-ndk-r9/platforms/android-8/arch-arm -fpic -funwind-tables -finline-limit=64 -fsigned-char -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=neon -fdata-sections -ffunction-sections -Wa,--noexecstack " in the CMakeCache.txt, but with the built libs, I didn't found any improvement with my test app, any one can help? thanks a lot!