On Wed 08-07-15 16:36:14, David Rientjes wrote: > On Wed, 8 Jul 2015, Michal Hocko wrote: > > > From: Michal Hocko <mhocko@xxxxxxx> > > > > OOM killer might be triggered explicitly via sysrq+f. This is supposed > > to kill a task no matter what e.g. a task is selected even though there > > is an OOM victim on the way to exit. This is a big hammer for an admin > > to help to resolve a memory short condition when the system is not able > > to cope with it on its own in a reasonable time frame (e.g. when the > > system is trashing or the OOM killer cannot make sufficient progress) > > > > E.g. it doesn't make any sense to obey panic_on_oom setting because > > a) administrator could have used other sysrqs to achieve the > > panic/reboot and b) the policy would break an existing usecase to > > kill a memory hog which would be recoverable unlike the panic which > > might be configured for the real OOM condition. > > > > It also doesn't make much sense to panic the system when there is no > > OOM killable task because administrator might choose to do additional > > steps before rebooting/panicking the system. > > > > While we are there also add a comment explaining why > > sysctl_oom_kill_allocating_task doesn't apply to sysrq triggered OOM > > killer even though there is no explicit check and we subtly rely > > on current->mm being NULL for the context from which it is triggered. > > > > Also be more explicit about sysrq+f behavior in the documentation. > > > > Signed-off-by: Michal Hocko <mhocko@xxxxxxx> > > Nack, this is already handled by patch 2 in my series. I understand that I guess you mean patch#3 > the titles were wrong for patches 2 and 3, but it doesn't mean we need to > add hacks around the code before organizing this into struct oom_control It is much easier to backport _fixes_ into older kernels (and yes I do care about that) if they do not depend on other cleanups. So I do not understand your point here. Besides that the cleanup really didn't make much change to the actuall fix because one way or another you still have to add a simple condition to rule out a heuristic/configuration which doesn't apply to sysrq+f path. So I am really lost in your argumentation here. > or completely pointless comments and printks that will fill the kernel > log. Could you explain what is so pointless about a comment which clarifies the fact which is not obviously visible from the current function? Also could you explain why the admin shouldn't get an information if sysrq+f didn't kill anything because no eligible task has been found? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>