* Michal Hocko <mhocko@xxxxxxxxxx> [170731 10:49]: > On Mon 31-07-17 07:37:35, Matthew Wilcox wrote: > > On Mon, Jul 31, 2017 at 04:08:10PM +0200, Michal Hocko wrote: > > > On Mon 31-07-17 09:56:48, Liam R. Howlett wrote: > [...] > > > > My focus on hugetlb is that it can stop the automatic recovery of the > > > > system. > > > > > > How? > > > > Let me try to explain the situation as I understand it. > > > > The customer has purchased a 128TB machine in order to run a database. > > They reserve 124TB of memory for use by the database cache. Everything > > works great. Then a 4TB memory module goes bad. The machine reboots > > itself in order to return to operation, now having only 124TB of memory > > and having 124TB of memory reserved. It OOMs during boot. The current > > output from our OOM machinery doesn't point the sysadmin at the kernel > > command line parameter as now being the problem. So they file a priority > > 1 problem ticket ... > > Well, I would argue that the oom report is quite clear that the hugetlb > memory has consumed the large part if not whole usable memory and that > should give a clue... Can you please show me where it's clear? Are you referring to these messages? Node 0 hugepages_total=15999 hugepages_free=15999 hugepages_surp=0 hugepages_size=8192kB Node 1 hugepages_total=16157 hugepages_free=16157 hugepages_surp=0 hugepages_size=8192kB I'm not trying to be obtuse, I'm just not sure what message in which you are referring. > > Nevertheless, I can see some merit here, but I am arguing that there > is simply no good way to handle this without admin involvement > unless we want to risk other and much more subtle breakage where the > application really expects it can consume the preallocated hugetlb pool > completely. And I would even argue that the later is more probable than > unintended memory failure reboot cycle. If somebody can tune hugetlb > pool dynamically I would recommend doing so from an init script. I agree that an admin involvement is necessary for a full recovery but I'm trying to make the best of a bad situation. Why can't it consume the preallocated hugetlb pool completely? I'm just trying to make the pool a little smaller. I thought that when the application fails to allocate a hugetlb it would receive a failure and need to cope with the allocation failure? Thanks, Liam -- 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>
