I got the reply from expert team:
"
There are multiple factors at play for the performance on Android L 5.x, and it should not be expected to reach Android K 4.x levels, due to item #2 below:
1) There was a 2D performance drop in the GPU driver related to the Linux kernel CMA. This has been fixed in 5.0.11p8 for the Android M 6.x BSP, and it has been fixed in the latest patch release of 5.0.11p7 in the Android L 5.1.1_2.1.0-GA BSP. So the customer can upgrade to the 5.1.1_2.1.0-GA to get a 2D performance boost.
2) There is a workaround for ARM Errata 845369 introduced in the Android L 5.x BSPs, which has a performance impact on all memcpy and memset. This brings an overall graphics performance degradation, but it is not recommended to remove this errata workaround, as it is known to cause stability issues.
3) The customer should try to enable the 'force GPU rendering' developer option in Android, as it has been seen to give significant performance increases in some applications on Android 5.x . Performance boost depends on the application, whether it already requests GPU acceleration in its manifest or not.
"