On Mon 22-05-17 14:04:15, Mike Snitzer wrote: > On Mon, May 22 2017 at 11:03am -0400, > Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > On Mon 22-05-17 10:52:44, Mikulas Patocka wrote: > > > > > > > > > On Mon, 22 May 2017, Michal Hocko wrote: > > [...] > > > > I am not sure I understand. OOM killer is invoked for _all_ allocations > > > > <= PAGE_ALLOC_COSTLY_ORDER that do not have __GFP_NORETRY as long as the > > > > OOM killer is not disabled (oom_killer_disable) and that only happens > > > > from the PM suspend path which makes sure that no userspace is active at > > > > the time. AFAIU this is a userspace triggered path and so the later > > > > shouldn't apply to it and GFP_KERNEL should be therefore sufficient. > > > > Relying to a portion of memory reserves to prevent from deadlock seems > > > > fundamentaly broken to me. > > > > > > > > > > The lvm2 was designed this way - it is broken, but there is not much that > > > can be done about it - fixing this would mean major rewrite. The only > > > thing we can do about it is to lower the deadlock probability with > > > __GFP_HIGH (or PF_MEMALLOC that was used some times ago). > > Yes, lvm2 was originally designed to to have access to memory reserves > to ensure forward progress. But if the mm subsystem has improved to > allow for the required progress without lvm2 trying to stake a claim on > those reserves then we'll gladly avoid (ab)using them. > > > But let me repeat. GFP_KERNEL allocation for order-0 page will not fail. > > OK, but will it be serviced immediately? Not failing isn't useful if it > never completes. Well, GFP_KERNEL will not guarantee an immediate success of course. There is nothing like that. Nor __GFP_HIGH will guarantee that, though, because reserves can get easily depleted by some workloads. You would have to use a dedicated memory pool to accomplish what you really need. -- 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>
