Messages in this thread | | | Subject | Re: Let's talk about the elephant in the room - the Linux kernel's inability to gracefully handle low memory pressure | From | "Artem S. Tashkinov" <> | Date | Mon, 5 Aug 2019 12:01:43 +0000 |
| |
On 8/5/19 9:05 AM, Hillf Danton wrote: > > On Sun, 4 Aug 2019 09:23:17 +0000 "Artem S. Tashkinov" <aros@gmx.com> wrote: >> Hello, >> >> There's this bug which has been bugging many people for many years >> already and which is reproducible in less than a few minutes under the >> latest and greatest kernel, 5.2.6. All the kernel parameters are set to >> defaults. > > Thanks for report! >> >> Steps to reproduce: >> >> 1) Boot with mem=4G >> 2) Disable swap to make everything faster (sudo swapoff -a) >> 3) Launch a web browser, e.g. Chrome/Chromium or/and Firefox >> 4) Start opening tabs in either of them and watch your free RAM decrease > > We saw another corner-case cpu hog report under memory pressure also > with swap disabled. In that report the xfs filesystem was an factor > with CONFIG_MEMCG enabled. Anything special, say like > > kernel:watchdog: BUG: soft lockup - CPU#7 stuck for 22s! [leaker1:7193] > or > [ 3225.313209] Xorg: page allocation failure: order:4, mode:0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0 > > in your kernel log?
I'm running ext4 only without LVM, encryption or anything like that. Plain GPT/MBR partitions with plenty of free space and no disk errors.
>> >> Once you hit a situation when opening a new tab requires more RAM than >> is currently available, the system will stall hard. You will barely be >> able to move the mouse pointer. Your disk LED will be flashing >> incessantly (I'm not entirely sure why). You will not be able to run new >> applications or close currently running ones. > > A cpu hog may come on top of memory hog in some scenario.
It might have happened as well - I couldn't know since I wasn't able to open a terminal. Once the system recovered there was no trace of anything extraordinary.
>> >> This little crisis may continue for minutes or even longer. I think >> that's not how the system should behave in this situation. I believe >> something must be done about that to avoid this stall. > > Yes, Sir. >> >> I'm almost sure some sysctl parameters could be changed to avoid this >> situation but something tells me this could be done for everyone and >> made default because some non tech-savvy users will just give up on >> Linux if they ever get in a situation like this and they won't be keen >> or even be able to Google for solutions. > > I am not willing to repeat that it is hard to produce a pill for all > patients, but the info you post will help solve the crisis sooner. > > Hillf >
In case you have troubles reproducing this bug report I can publish a VM image - still everything is quite mundane: Fedora 30 + XFCE + web browser. Nothing else, nothing fancy.
Regards, Artem
| |