Date:   Fri, 30 Oct 2020 04:17:07 +0000
From:   NASA Jeff <tallboy258@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: Freezing between .48 and .51 when hitting swap.

I have an issue on my laptop which is old but with 2.5gb of ram an ssd hdd and using zram compression I believe.
When ever it hits swap the system completely locks up and I have to reboot.
This only started occurring in .51
I only have access to my phone at the moment though I’ve looked at the code and have what I believe is a workable solution that should mitigate against and future issues. The code base looked a little old so was probably quite stable but it really could do with some modernisation.
The issue was with the active app in user space.
What needs to be done is to swap out inactive pages in background user apps prior to the active apps hitting the memory threshold which was causing the lockup to occure.

An improvement on the existing code would be to swap in and out inactive pages gradually so as to avoid any heavy system load.

It may also be an idea to set the up priority to near idel for such heavy io background processes so that the overlapping io doesn’t cause issues with user space io.

I believe this is similar to the main Linux scheduler since bfs because implementing a script to renice processes that started hitting higish cpu and then again when their cpu dipped didn’t seem to make much difference. It was unclear if this was also implemented for cocurent io as the window managers now seem to queue io tasks instead of executing them concurrently. Concurrent io was at least a historic issue.

Kind regards,
Oliverthered 

Sent from my iPhone

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