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The PELT _sum values are a saw-tooth function, dropping on the decay edge and then growing back up again during the window. When these window-edges are not aligned between cfs_rq and se, we can have the situation where, for example, on dequeue, the se decays first. Its _sum values will be small(er), while the cfs_rq _sum values will still be on their way up. Because of this, the subtraction: cfs_rq->avg._sum -= se->avg._sum will result in a positive value. This will then, once the cfs_rq reaches an edge, translate into its _avg value jumping up. This is especially visible with the runnable_load bits, since they get added/subtracted a lot. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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.