Messages in this thread | | | From | Daniel Drake <> | Date | Fri, 23 Aug 2019 10:14:52 +0800 | Subject | Re: Let's talk about the elephant in the room - the Linux kernel's inability to gracefully handle low memory pressure |
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On Fri, Aug 23, 2019 at 9:54 AM ndrw <ndrw.xf@redhazel.co.uk> wrote: > That's obviously a lot better than hard freezes but I wouldn't call such > system lock-ups an excellent result. PSI-triggered OOM killer would have > indeed been very useful as an emergency brake, and IMHO such mechanism > should be built in the kernel and enabled by default. But in my > experience it does a very poor job at detecting imminent freezes on > systems without swap or with very fast swap (zram).
Perhaps you could share your precise test environment and the PSI condition you are expecting to hit (that is not being hit). Except for the single failure report mentioned, it's been working fine here in all setups, including with zram which is shipped out of the box.
The nice thing about psi is that it's based on how much real-world time the kernel is spending doing memory management. So it's very well poised to handle differences in swap speed etc. You effectively just set the threshold for how much time you view as excessive for the kernel to be busy doing MM, and psi tells you when that's hit.
> > There's just one issue we've seen so far: a single report of psi reporting > > memory pressure on a desktop system with 4GB RAM which is only running > > the normal desktop components plus a single gmail tab in the web browser. > > psi occasionally reports high memory pressure, so then psi-monitor steps in and > > kills the browser tab, which seems erroneous. > > Is it Chrome/Chromium? If so, that's a known bug > (https://bugs.chromium.org/p/chromium/issues/detail?id=333617)
The issue does not concern which process is being killed. The issue is that in the single report we have of this, psi is apparently reporting high memory pressure even though the system has plenty of free memory.
Daniel
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