> On Thu, 19 Aug 2010, KOSAKI Motohiro wrote: > > > > No, I'm talking about threads with CLONE_VM and not CLONE_THREAD (or > > > CLONE_VFORK, in your example). They share the same address space but are > > > in different tgid's and may sit holding mm->mmap_sem looping in the page > > > allocator while we know we're oom and there's no chance of freeing any > > > more memory since the oom killer doesn't kill will other tasks have yet to > > > exit. > > > > Why don't you use pthread library? Is there any good reason? That said, > > If you are trying to optimize neither thread nor vfork case, I'm not charmed > > this because 99.99% user don't use it. but even though every user will get > > performance degression. Can you please consider typical use case optimization? > > > > Non-NPTL threaded applications exist in the wild, and I can't change that. Which application? If it is major opensource application, I think this one makes end user happy. > This mm->mmap_sem livelock is a problem for them, we've hit it internally > (we're forced to carry this patch internally), and we aren't the only ones > running at least some non-NPTL apps. That's why this code existed in the > oom killer for over eight years since the 2.4 kernel before you removed it > based on the mempolicy policy of killing current, which has since been > obsoleted. Until CLONE_VM without CLONE_THREAD is prohibited entirely on > Linux, this livelock can exist. Or, can you eliminate O(n^2) thing? The cost is enough low, I don't oppose this. > Users who do not want the tasklist scan here, which only iterates over > thread group leaders and not threads, can enable > /proc/sys/vm/oom_kill_allocating_task. That's its whole purpose. Other > than that, the oom killer will never be the most efficient part of the > kernel and doing for_each_process() is much less expensive than all the > task_lock()s we take already. No. Please don't forget typical end user don't use any kernel knob. kernel knob is not a way for developer excuse. -- 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>