Re: ext2/zram issue [was: Linux 5.19]

From: Jiri Slaby
Date: Tue Aug 09 2022 - 08:36:07 EST


On 09. 08. 22, 11:20, Sergey Senozhatsky wrote:
On (22/08/09 18:11), Sergey Senozhatsky wrote:
/me needs to confirm.

With that commit reverted, I see no more I/O errors, only oom-killer
messages (which is OK IMO, provided I write 1G of urandom on a machine w/
800M of RAM):

Hmm... So handle allocation always succeeds in the slow path? (when we
try to allocate it second time)

Yeah I can see how handle re-allocation with direct reclaim can make it more
successful, but in exchange it oom-kills some user-space process, I suppose.
Is oom-kill really a good alternative though?

We likely will need to revert e7be8d1dd983 given that it has some
user visible changes. But, honestly, failing zram write vs oom-kill
a user-space is a tough choice.

Note that it OOMs only in my use case -- it's obviously too large zram on too low memory machine.

But the installer is different. It just creates memory pressure, yet, reclaim works well and is able to find memory and go on. I would say atomic vs non-atomic retry in the original (pre-5.19) approach makes the difference.

And yes, we should likely increase the memory in openQA to avoid too many reclaims...

PS the kernel finished building, now images are built, hence the new openQA run hasn't started yet. I will send the revert when it's complete and all green.

thanks,
--
js
suse labs