On Thu, Jul 26, 2018 at 08:10:41AM +0200, Tino Lehnig wrote: > 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
That means you could reproduce it without writeback feature? If so, it would be more reasoanble to check [0bcac06f27d75, skip swapcache for swapin of synchronous device] > 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. Thanks. I will try it later today.
