Following the idea that it's some interaction with the X server, I further noticed that switching out of X to a text virtual console makes the page-outs stop. Going back to the X VT, the page-outs resume. I've attached another set of vmstat logs for the following timeline: 1580290800 System is running Xorg, stress to limit memory, and dd to exercise the buffer cache, with constant page-outs 1580290810 Switch to a text virtual console - page-outs stop 1580290830 Switch back to X VT - page-outs resume I'm vaguely suspecting something to do with the way Xorg handles old-fashioned programs that do CPU-driven bitmap-based rendering, as my desktop does typically have a lot of these (urxvt instances, xosview, the Notion window manager itself) - maybe they cause some particular pattern of memory churn in the X server, and perhaps only with certain video drivers...could Xorg perhaps wrongly madvise() the kernel about certain memory? It seems notable that having glxgears should cause the page-outs to stop. However, even a minimal X session with a sakura or qterminal window seems to show some degree of needless page-outs with low memory and busy cache, though not as severe - however, it's difficult to avoid observer effects! There did seem to be a notable pattern of increasing swap utilisation when switching away from the X VT, and a drop in swap utilisation when switching back to X. Should I perhaps take it up with the Xorg people instead? -- Chris
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vmstat_5.5.0-rc6_unpatched_cedwards_2020-01-29.tar.gz
Description: vmstat_5.5.0-rc6_unpatched_cedwards_2020-01-29.tar.gz
