On Sat, Feb 21, 2015 at 08:12:08PM +0900, Tetsuo Handa wrote: > My main issue is > > c) whether to oom-kill more processes when the OOM victim cannot be > terminated presumably due to the OOM killer deadlock. > > Dave Chinner wrote: > > On Fri, Feb 20, 2015 at 07:36:33PM +0900, Tetsuo Handa wrote: > > > Dave Chinner wrote: > > > > I really don't care about the OOM Killer corner cases - it's > > > > completely the wrong way line of development to be spending time on > > > > and you aren't going to convince me otherwise. The OOM killer a > > > > crutch used to justify having a memory allocation subsystem that > > > > can't provide forward progress guarantee mechanisms to callers that > > > > need it. > > > > > > I really care about the OOM Killer corner cases, for I'm > > > > > > (1) seeing trouble cases which occurred in enterprise systems > > > under OOM conditions > > > > You reach OOM, then your SLAs are dead and buried. Reboot the > > box - its a much more reliable way of returning to a working system > > than playing Russian Roulette with the OOM killer. > > What Service Level Agreements? Such troubles are occurring on RHEL systems > where users are not sitting in front of the console. Unless somebody is > sitting in front of the console in order to do SysRq-b when troubles > occur, the down time of system will become significantly longer. > > What mechanisms are available for minimizing the down time of system > when troubles under OOM condition occur? Software/hardware watchdog? > Indeed they may help, but they may be triggered prematurely when the > system has not entered into the OOM condition. Only the OOM killer knows. # echo 1 > /proc/sys/vm/panic_on_oom .... > We have memory cgroups to reduce the possibility of triggering the OOM > killer, though there will be several bugs remaining in RHEL kernels > which make administrators hesitate to use memory cgroups. Fix upstream first, then worry about vendor kernels. .... > Not only we cannot expect that the OOM killer messages being saved to > /var/log/messages under the OOM killer deadlock condition, but also CONFIG_PSTORE=y and configure appropriately from there. > we do not emit the OOM killer messages if we hit So add a warning. > If you want to stop people from playing Russian Roulette with the OOM > killer, please remove the OOM killer code entirely from RHEL kernels so that > people must use their systems with hardcoded /proc/sys/vm/panic_on_oom == 1 > setting. Can you do it? No. You need to go through vendor channels to get a vendor kernel config change made. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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>