Messages in this thread | | | Subject | Re: Zram writeback feature unstable with heavy swap utilization - BUG: Bad page state in process... | From | Tino Lehnig <> | Date | Thu, 26 Jul 2018 08:10:41 +0200 |
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Hi,
On 07/26/2018 04:03 AM, Minchan Kim wrote: > A thing I could imagine is > [0bcac06f27d75, skip swapcache for swapin of synchronous device] > It was merged into v4.15. Could you check it by bisecting?
Thanks, I will check that.
>> My operating system is a minimal install of Debian 9. I took the kernel >> configuration from the default Debian kernel and built my own kernel with >> "make oldconfig" leaving all settings at their defaults. The only thing I >> changed in the configuration was enabling the zram writeback feature. > > You mean you changed host kernel configuration? > >> >> All my tests were done on bare-metal hardware with Xeon processors and lots >> of RAM. I encounter the bug quite quickly, but it still takes several GBs of >> swap usage. Below is my /proc/meminfo with enough KVM instances running (3 >> in my case) to trigger the bug on my test machine. > > Aha.. you did writeback feature into your bare-metal host machine and execute > kvm with window images as a guest. So, PG_uptodate warning happens on host side, > not guest? Right?
Yes, I am only talking about the host kernel. Zram swap is set up on the host. I just used Windows guests to fill up the host RAM and force it into swap.
>> I will also try to reproduce the problem on some different hardware next.
Just to confirm, I was able to reproduce the problem on another machine running Ubuntu 18.04 with the Ubuntu stock kernel (4.15) and no modifications to the kernel configuration whatsoever. The host had 8 GB of RAM, 32 GB of swap with zram and a 32 GB SSD as backing device. I had to start only one Windows VM with "-m 32768" to trigger the bug.
-- Kind regards,
Tino Lehnig
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