On Thu 19-02-15 22:29:37, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Thu 19-02-15 06:01:24, Johannes Weiner wrote: > > [...] > > > Preferrably, we'd get rid of all nofail allocations and replace them > > > with preallocated reserves. But this is not going to happen anytime > > > soon, so what other option do we have than resolving this on the OOM > > > killer side? > > > > As I've mentioned in other email, we might give GFP_NOFAIL allocator > > access to memory reserves (by giving it __GFP_HIGH). This is still not a > > 100% solution because reserves could get depleted but this risk is there > > even with multiple oom victims. I would still argue that this would be a > > better approach because selecting more victims might hit pathological > > case more easily (other victims might be blocked on the very same lock > > e.g.). > > > Does "multiple OOM victims" mean "select next if first does not die"? > Then, I think my timeout patch http://marc.info/?l=linux-mm&m=142002495532320&w=2 > does not deplete memory reserves. ;-) It doesn't because --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2603,9 +2603,7 @@ gfp_to_alloc_flags(gfp_t gfp_mask) alloc_flags |= ALLOC_NO_WATERMARKS; else if (in_serving_softirq() && (current->flags & PF_MEMALLOC)) alloc_flags |= ALLOC_NO_WATERMARKS; - else if (!in_interrupt() && - ((current->flags & PF_MEMALLOC) || - unlikely(test_thread_flag(TIF_MEMDIE)))) + else if (!in_interrupt() && (current->flags & PF_MEMALLOC)) alloc_flags |= ALLOC_NO_WATERMARKS; you disabled the TIF_MEMDIE heuristic and use it only for OOM exclusion and break out from the allocator. Exiting task might need a memory to do so and you make all those allocations fail basically. How do you know this is not going to blow up? > If we change to permit invocation of the OOM killer for GFP_NOFS / GFP_NOIO, > those who do not want to fail (e.g. journal transaction) will start passing > __GFP_NOFAIL? > > -- > 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> -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
