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). But let me repeat. GFP_KERNEL allocation for order-0 page will not fail. If you need non-failing semantic then just make it clear by adding __GFP_NOFAIL rather than __GFP_HIGH. Memory reserves are a scarce resource and there are users which might really need it from atomic contexts. Anyway, this is not the code I am maintaining so I will not argue more and won't nack the patch. But is smells like a pure cargo cult, to be honest. If you really insist, though, I would just ask to have a more detailed explanation why it is _believed_ the flag is needed because the vague "Use __GFP_HIGH to avoid low memory issues when a device is suspended and the ioctl is needed to resume it." doesn't really clarify much to be honest. Thanks! -- 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>
