Calling printk() people. ;-) On 2018/10/12 21:41, Johannes Weiner wrote: > On Fri, Oct 12, 2018 at 09:10:40PM +0900, Tetsuo Handa wrote: >> On 2018/10/12 21:08, Michal Hocko wrote: >>>> So not more than 10 dumps in each 5s interval. That looks reasonable >>>> to me. By the time it starts dropping data you have more than enough >>>> information to go on already. >>> >>> Yeah. Unless we have a storm coming from many different cgroups in >>> parallel. But even then we have the allocation context for each OOM so >>> we are not losing everything. Should we ever tune this, it can be done >>> later with some explicit examples. >>> >>>> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> >>> >>> Thanks! I will post the patch to Andrew early next week. >>> >> >> How do you handle environments where one dump takes e.g. 3 seconds? >> Counting delay between first message in previous dump and first message >> in next dump is not safe. Unless we count delay between last message >> in previous dump and first message in next dump, we cannot guarantee >> that the system won't lockup due to printk() flooding. > > How is that different from any other printk ratelimiting? If a dump > takes 3 seconds you need to fix your console. It doesn't make sense to > design KERN_INFO messages for the slowest serial consoles out there. You can't fix the console. It is a hardware limitation. > > That's what we did, btw. We used to patch out the OOM header because > our serial console was so bad, but obviously that's not a generic > upstream solution. We've since changed the loglevel on the serial and > use netconsole[1] for the chattier loglevels. > > [1] https://github.com/facebook/fbkutils/tree/master/netconsd >
