> On Mon, 15 Feb 2010, KOSAKI Motohiro wrote: > > > > Two VM sysctls, oom dump_tasks and oom_kill_allocating_task, were > > > implemented for very large systems to avoid excessively long tasklist > > > scans. The former suppresses helpful diagnostic messages that are > > > emitted for each thread group leader that are candidates for oom kill > > > including their pid, uid, vm size, rss, oom_adj value, and name; this > > > information is very helpful to users in understanding why a particular > > > task was chosen for kill over others. The latter simply kills current, > > > the task triggering the oom condition, instead of iterating through the > > > tasklist looking for the worst offender. > > > > > > Both of these sysctls are combined into one for use on the aforementioned > > > large systems: oom_kill_quick. This disables the now-default > > > oom_dump_tasks and kills current whenever the oom killer is called. > > > > > > The oom killer rewrite is the perfect opportunity to combine both sysctls > > > into one instead of carrying around the others for years to come for > > > nothing else than legacy purposes. > > > > "_quick" is always bad sysctl name. > > Why? It does exactly what it says: it kills current without doing an > expensive tasklist scan and suppresses the possibly long tasklist dump. > That's the oom killer's "quick mode." Because, an administrator think "_quick" implies "please use it always". plus, "quick" doesn't describe clealy meanings. oom_dump_tasks does. > > instead, turnning oom_dump_tasks on > > by default is better. > > > > It's now on by default and can be disabled by enabling oom_kill_quick. > > > plus, this patch makes unnecessary compatibility issue. > > > > It's the perfect opportunity when totally rewriting the oom killer to > combine two sysctls with the exact same users into one. Users will notice > that the tasklist is always dumped now (we're defaulting oom_dump_tasks > to be enabled), so there is no reason why we can't remove oom_dump_tasks, > we're just giving them a new way to disable it. oom_kill_allocating_task > no longer always means what it once did: with the mempolicy-constrained > oom rewrite, we now iterate the tasklist for such cases to kill a task. > So users need to reassess whether this should be set if all tasks on the > system are constrained by mempolicies, a typical configuration for > extremely large systems. No. Your explanation doesn't answer why this change don't cause any comatibility issue to _all_ user. Merely "opportunity" doesn't allow we ignore real world user. I had made some incompatibility patch too, but all one have unavoidable reason. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>