Hi! > I encountered the following problem. We use short expiration time for > kerberos contexts created by rpc.gssd (some patches were included in mainline > nfs-utils). In particular, we use 120secs expiration time. > > Now, I run application that eats 80% of available RAM. Then I run 10 parallel > dd processes that write data into NFS4 volume with sec=krb5. > > As soon as the kerberos context expires (i.e., up to 120 secs), the whole > system gets stuck in do_page_fault and succesive functions. It is because > there is no free memory in kernel, all free memory is used as cache for NFS4 > (due to dd traffic), kernel ask NFS to write back its pages but NFS cannot do > anything as it is missing valid context. NFS contacts rpc.gssd to provide > a renewed context, the rpc.gssd does not provide the context as it needs some memory > to scan /tmp for a ticket. I.e., it deadlocks. > > Longer context expiration time is no real solution as it only makes the > deadlock less often. > > Any ideas what can be done here? (Please cc me.) We could preallocate some > memory in rpc.gssd and use mlockall but not sure whether this proctects also > kernel malloc for things related to rpc.gssd and context creation (new file > descriptors and so on). > > This is seen in 2.6.32 kernel but most probably this is related to all kernel > versions. Seems like pretty fundamental problem in nfs :-(. Limiting writeback caches for nfs, so that system has enough memory to perform rpc calls with the rest might do the trick, but... -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
