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Psi monitor aims to provide a low-latency short-term pressure detection mechanism configurable by users. It allows users to monitor psi metrics growth and trigger events whenever a metric raises above user-defined threshold within user-defined time window. Time window and threshold are both expressed in usecs. Multiple psi resources with different thresholds and window sizes can be monitored concurrently. Psi monitors activate when system enters stall state for the monitored psi metric and deactivate upon exit from the stall state. While system is in the stall state psi signal growth is monitored at a rate of 10 times per tracking window. Min window size is 500ms, therefore the min monitoring interval is 50ms. Max window size is 10s with monitoring interval of 1s. When activated psi monitor stays active for at least the duration of one tracking window to avoid repeated activations/deactivations when psi signal is bouncing. Notifications to the users are rate-limited to one per tracking window. Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> (not upstream yet, latest version published at: https://lore.kernel.org/patchwork/patch/1052418/) Conflicts: include/linux/psi.h kernel/cgroup/cgroup.c kernel/sched/psi.c (1. replaced __poll_t with unsigned int 2. replaced EPOLLERR/EPOLLPRI with POLLERR/POLLPRI (values are the same) 3. include <linux/cgroup-defs.h> in include/linux/psi.h 4. include <uapi/linux/sched/types.h> in kernel/sched/psi.c) Bug: 127712811 Bug: 129157727 Test: lmkd in PSI mode Change-Id: I1688f047e98e1f109627dad72a33d2f70e575268 Signed-off-by: Suren Baghdasaryan <surenb@google.com>
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.