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When stop is executed with EC=ESL=0, it appears to execute like a normal instruction (resuming from NIP when woken by interrupt). So all the save/restore handling can be avoided completely. In particular NV GPRs do not have to be saved, and MSR does not have to be switched back to kernel MSR. So move the test for EC=ESL=0 sleep states out to power9_idle_stop, and return directly to the caller after stop in that case. This improves performance for ping-pong benchmark with the stop0_lite idle state by 2.54% for 2 threads in the same core, and 2.57% for different cores. Performance increase with HV_POSSIBLE defined will be improved further by avoiding the hwsync. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.