On Fri 11-03-16 16:45:34, Vladimir Davydov wrote: > On Fri, Mar 11, 2016 at 01:51:05PM +0100, Michal Hocko wrote: > > On Fri 11-03-16 15:39:00, Vladimir Davydov wrote: > > > On Fri, Mar 11, 2016 at 12:54:50PM +0100, Michal Hocko wrote: > > > > On Fri 11-03-16 13:12:47, Vladimir Davydov wrote: > > > > > These fields are used for dumping info about allocation that triggered > > > > > OOM. For cgroup this information doesn't make much sense, because OOM > > > > > killer is always invoked from page fault handler. > > > > > > > > The oom killer is indeed invoked in a different context but why printing > > > > the original mask and order doesn't make any sense? Doesn't it help to > > > > see that the reclaim has failed because of GFP_NOFS? > > > > > > I don't see how this can be helpful. How would you use it? > > > > If we start seeing GFP_NOFS triggered OOMs we might be enforced to > > rethink our current strategy to ignore this charge context for OOM. > > IMO the fact that a lot of OOMs are triggered by GFP_NOFS allocations > can't be a good enough reason to reconsider OOM strategy. What I meant was that the global OOM doesn't trigger OOM got !__GFP_FS while we do in the memcg charge path. > We need to > know what kind of allocation fails anyway, and the current OOM dump > gives us no clue about that. We do print gfp_mask now so we know what was the charging context. > Besides, what if OOM was triggered by GFP_NOFS by pure chance, i.e. it > would have been triggered by GFP_KERNEL if it had happened at that time? Not really. GFP_KERNEL would allow to invoke some shrinkers which are GFP_NOFS incopatible. > IMO it's just confusing. > > > > > > Wouldn't it be better to print err msg in try_charge anyway? > > > > Wouldn't that lead to excessive amount of logged messages? > > We could ratelimit these messages. Slab charge failures are already > reported to dmesg (see ___slab_alloc -> slab_out_of_memory) and nobody's > complained so far. Are there any non-slab GFP_NOFS allocations charged > to memcg? I believe there might be some coming from FS via add_to_page_cache_lru. Especially when their mapping gfp_mask clears __GFP_FS. I haven't checked the code deeper but some of those might be called from the page fault path and trigger memcg OOM. I would have to look closer. -- Michal Hocko SUSE Labs -- 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>