> On Sun, 14 Nov 2010, KOSAKI Motohiro wrote: > > > > So the question that needs to be answered is: why do these threads deserve > > > to use 3% more memory (not >4%) than others without getting killed? If > > > there was some evidence that these threads have a certain quantity of > > > memory they require as a fundamental attribute of CAP_SYS_RAWIO, then I > > > have no objection, but that's going to be expressed in a memory quantity > > > not a percentage as you have here. > > > > 3% is choosed by you :-/ > > > > No, 3% was chosen in __vm_enough_memory() for LSMs as the comment in the > oom killer shows: > > /* > * Root processes get 3% bonus, just like the __vm_enough_memory() > * implementation used by LSMs. > */ > > and is described in Documentation/filesystems/proc.txt. > > I think in cases of heuristics like this where we obviously want to give > some bonus to CAP_SYS_ADMIN that there is consistency with other bonuses > given elsewhere in the kernel. Keep comparision apple to apple. vm_enough_memory() account _virtual_ memory. oom-killer try to free _physical_ memory. It's unrelated. > > > Old background is very simple and cleaner. > > > > The old heuristic divided the arbitrary badness score by 4 with > CAP_SYS_RESOURCE. The new heuristic doesn't consider it. > > How is that more clean? > > > CAP_SYS_RESOURCE mean the process has a privilege of using more resource. > > then, oom-killer gave it additonal bonus. > > > > As a side-effect of being given more resources to allocate, those > applications are relatively unbounded in terms of memory consumption to > other tasks. Thus, it's possible that these applications are using a > massive amount of memory (say, 75%) and now with the proposed change a > task using 25% of memory would be killed instead. This increases the > liklihood that the CAP_SYS_RESOURCE thread will have to be killed > eventually, anyway, and the goal is to kill as few tasks as possible to > free sufficient amount of memory. You are talking two difference at once. 3% vs 4x and CAP_SYS_RESOURCE and CAP_SYS_ADMIN. Please keep comparing apple to apple. > > Since threads having CAP_SYS_RESOURCE have full control over their > oom_score_adj, they can take the additional precautions to protect > themselves if necessary. It doesn't need to be a part of the heuristic to > bias these tasks which will lead to the undesired result described above > by default rather than intentionally from userspace. > > > CAP_SYS_RAWIO mean the process has a direct hardware access privilege > > (eg X.org, RDB). and then, killing it might makes system crash. > > > > Then you would want to explicitly filter these tasks from oom kill just as > OOM_SCORE_ADJ_MIN works rather than giving them a memory quantity bonus. No. Why does userland recover your mistake? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>