![]() ![]() Psi_full - the percentage of time that nobody is able to use the CPU for actual work due to memory pressureīy default, avg10 (10 seconds averaged) values are used. Psi_some - the percentage of the time that at least one process could be running if it weren't waiting for memory resources In modern Linux kernels, /proc/pressure/memory file provides information on the time that processes spend waiting due to memory pressure. Tasks in a system wait for contended hardware resources. ![]() PSI aggregates and reports the overall wallclock time in which the PSI (pressure stall information) observer This observer may require superuser rights to initialize and run. E.g., in case of 'low' trigger, the value will be 1, in case of all triggers active, the value will be equal to 7. sys/fs/cgroup/memory/cgroup.event_control is used to subscribe for events from /sys/fs/cgroup/memory/memory.pressure_level - this is a standard cgroups mechanism.Ĭgroups - bit mask ('critical - 'medium' - 'low'). "Memory pressure" eval is based on "scanned/reclaimed pages" ratio, see Linux kernel comments for details: CGroups subsystem allows us to set physical and virtual memory limits for the process or process group. This sets up cgroups 'memory_pressure' event file descriptor and subscribes for these events. Swp_tend - 'swap tendency' metric counted as described above. You can enable it with -showTendency option. So this method, unfortunately, is unusable in production, and that's why it is disabled by default. The actual problem is that 'swappines' is a standard system param, 'mapped ratio' can be counted from 'nr_mapped' system metric, but the 'distress' value is inaccessible from the kernel internals for user-space software. LowPassHalfLifeSeconds - low-pass filter half-life time (in seconds), default is 30.ĪverageOnl圜urrent - don't calculate average pages faults using statics collected by the OS before the program was started, use only new values (default: false).Įxample: -lowPassHalfLifeSeconds=15 -averageOnl圜urrent 'Swap tendency' calculatorĪnother task is to count 'swap tendency' metric, as it is described here This can be used for swap trashing evaluation. Swp_flts_mult- current page faults per second and average page faults per second ratio. Swp_flts_sec_f - page faults per second with EWMA low-pass filter Because sample times are inconsistent and we're measuring CPU time instead of real time, EWMA low-pass filter is applied for the values. In case if current faults per second value is significantly higher than the average, we can assume that swap trashing is happening. One task of this observer is to monitor 'pgmajfault' (page faults counter) parameter. To enable optional metrics, you can add a custom option to the command line like -showInactive -showReclaimable Page faults counter Mem_inactive - The total amount of buffer or page cache memory, that are free and and available (in megabytes) Mem_reclaim - Part of Slab, that might be reclaimed, such as caches (in megabytes) Swp_total - total swap spaces (in megabytes) Swp_free - free swap space (in megabytes) This can be used for "simple" memory pressure threshold-based evaluation. Mem_pcnt - percent of physical memory filling. Current Linux kernel versions count this in a slightly different way than in a previous metric. ![]() Mem_avail - the amount of memory that is available for a new workload, without pushing the system into swap, 'MemAvailable' param from /proc/meminfo file. This is counted using a legacy algorithm from Linux kernel, see patch description and code comments for the details and explanations. Mem_avail_est - the amount of memory that is available for a new workload, without pushing the system into swap, estimated from MemFree, Active(file), Inactive(file), and SReclaimable, as well as the "low" watermarks from /proc/zoneinfo file. Mem_total - total system physical memory (in megabytes) This reads and parses /proc/meminfo file and generates the following metrics: It consists of a few sub-components, that collect and analyze various metrics: /proc/meminfo observer This is a utility with a set of tests to explore and compare different ways of detecting ‘memory pressure’ (the system is running out of free memory) state in Linux kernel-based OS. ![]()
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