Hi Derek, Thank you to raise this issue. We will fix it and add back the --hash original functionality. Thanks Steven From: Lin, Derek (HPS SW) [mailto:derek.lin2@hpe.com] Sent: Friday, September 20, 2019 2:54 PM To: devel@edk2.groups.io Cc: Feng, Bob C ; Shi, Steven Subject: BaseTools --hash malfunction after migrate from stable201905 to stable201908 Hi BaseTools experts, We saw the clean build performance improvement after updating from edk2-stable201905 to edk2-stable201908, which is promising. But we found the incremental build time increase 25%~35%, which is not good. We're building server platform. And we use --hash to speed up incremental build as described in https://github.com/BobCF/edk2/wiki/Incremental-Build After upgrading to edk2-stable201908, none of AutoGen is skipped when I did an incremental build without any code change. Dig into the issue, it is caused by commit https://github.com/tianocore/edk2/commit/0e7e7a264cd80ab71ea0f9e9da2d0617d4b539c4 >From the code change logic, it seems like it require both --hash and --binary-source to perform cache based incremental build. However, when we only have --hash in build flag, it is not functional. Here's a build time log retrieved from -y report.log. 201905 incremental | 201908 incremental | 201905 clean | 201908 clean Build Duration: 00:03:44 00:04:40 00:07:12 00:06:19 AutoGen Duration: 00:02:40 00:03:15 00:04:28 00:03:09 Make Duration: 00:00:36 00:00:39 00:01:21 00:01:34 GenFds Duration: 00:00:27 00:00:28 00:01:22 00:01:18 We could see the AutoGen Duration has almost no change between clean and incremental build in 201908. Could we fix this? Thanks, Derek