Tip for Desktop Memory management, new vm tuning option

[Liam Proven]

On Tue, 30 Jul 2019 at 14:43, Rashkae <ubuntu at tigershaunt.com> wrote:
>
> Recent Linux Kernels since Ubuntu 16.04 have had changes to Virtual
> Memory management that drastically hurt performance on Desktop loads
> where RAM is not always sufficient for all running apps.  With 4 to 8 GB
> desktops it's easy, if multi-tasking, to starve the RAM.  With older V3
> and 4.4 Linux kernels, swap on an SSD, you could easily drive the system
> memory usage several GB past your RAM and not even notice.
>
> However, with Newer linux kernels, if memory usage approaches your RAM,
> applications that try to allocate a large chunk of memory could quickly
> send a system into a swap tailspin that renders the system inoperable
> until rebooted or processes manually killed.  I've tripped over this
> several times over the past few years, and I finally found the change
> that causes it, Documented Here:
>
> https://www.fclose.com/linux-kernels/642756/mm-scale-kswapd-watermarks-in-proportion-to-memory-linux-4-6/
>
> The key to avoiding this swap lock problem is to increase
> /proc/sys/vm/watermark_scale_factor
>
> It defaults to 10.  In my testing, 100 is still not enough to avoid the
> problems, but increasing it to 500 *drastically* improves the computer's
> ability to handle memory over-commit without falling on it's face.
>
> On my 8GB system, I can have several browser windows, thunderbird, Open
> Office, calibre and a few movies playing, (brining my RAM usage past
> 6GB), then open a 4GB Windows 10 VirtualBox instance, and everything
> works with no noticeable slowdowns or hitches.  This was completely
> impossible before.
>
> If you want to try this, the change can be made permanent by adding this
> line in /etc/sysctl.conf.  Run sudo sysctl --system to apply changes
> without reboot.
>
>
> vm.watermark_scale_factor=500

_Very_ interesting. Thanks for that. I will try it. I have been
experiencing related problems myself recently. I tried this and noted
by assigned-memory meter leap up instantly. I have 16 GB but my normal
workload is ITRO 12-14GB.

I upgraded to a 16GB machine because with 6-7GB on my previous 8GB
machine, it was bogging down badly. I experimented with swappiness
settings and compcache but could not get any real improvement.


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