Rich Freeman via plug on 20 May 2020 10:34:33 -0700 |
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Re: [PLUG] memory usage in Linux |
On Tue, May 19, 2020 at 2:35 PM Eric Lucas via plug <plug@lists.phillylinux.org> wrote: > > I'm running Kubuntu 18.04 [1] on a Dell Laptop with a 2-core i7 [2] and 16 GB of RAM (the max apparently.) > I tend to leave lots of windows open on two or three of my four virtual desktops. > Sometimes things get slow (like participating in a zoom chat with a few dozen fellow homebrewers last night.) > I installed 'cockpit' to see what's up. All is okay except for RAM. It shows near 16GB of RAM used. > I seem to recall (from years ago) that Linux "hoovers up" all the RAM and then parcels it out to applications as needed. > If so, what's the point of telling me how much RAM I have used if it's always 99+%? > How do others monitor and/or manage RAM usage in Linux? > Here is a typical output of the "free" command: free total used free shared buff/cache available Mem: 16373372 8077212 2613968 2766012 5682192 5184788 Swap: 0 0 0 Total is just the amount of RAM in the system - 16GB in this case (same as with you). Used is total - free - buffers - cache. Available is what is available for use, taking into account reclaiming buffers and cache. It isn't the same as total - used because not all of this memory can be reclaimed. This is what I would probably focus on when monitoring. Free is memory that is completely unused. As you say the kernel tries to minimize this, but if a big process dies there will be free ram until it gets filled with cache/etc, which won't happen until there is IO. I would just focus on available memory from a memory management standpoint. I'm sure there are GUI applications that can monitor this as well. MemAvailable also shows up in /proc/meminfo. Monitoring swap use is also important, but you really want to see how much is swapping in and out - a slow memory leak might lead to a bunch of swap getting used and isn't ideal, but probably won't impact actual performance. -- Rich ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug