Description of problem: We get on the client side a memory leak on the size-8192 buckets when running under a NFSV4 mount the bench iozone with -U option in a infinite loop. We can see with "slabtop -s c" the number of size-8192 buckets constantly increases without never decreases. At the beginning : 33 33 100% 8.00K 33 1 264K size-8192 After half and hour: 89 89 100% 8.00K 89 1 712K size-8192 After one hour: 174 172 98% 8.00K 174 1 1392K size-8192 After two hours: 302 300 99% 8.00K 302 1 2416K size-8192 After four hours: 533 533 100% 8.00K 533 1 4264K size-8192 After six hours and half: 804 804 100% 8.00K 804 1 6432K size-8192 Version-Release number of selected component (if applicable): Linux version 2.6.18-53.el5 (brewbuilder.redhat.com) (gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)) #1 SMP Wed Oct 10 16:34:19 EDT 2007 How reproducible: Do the nfsv4 mount and run with the mounted directory: It is possible to reproduce it on one machine with a NFSV4 mount in loopback. For example on the machine nfs1gb machine: mount -t nfs4 nfs1gb:/ /mnt/nosec while true; do ./iozone -+q 30 -ace -r 64 -i 0 -i 1 -i 2 -f /mnt/nosec/nfs1_nfs4_gb -U /mnt/nosec; date; sleep 30; done The nfs1gb machine used is a Intel X86_64 64bits two-ways. Best Regards Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info:
Finally got a chance to look over this today. I see a similar memory leak when just mounting and unmounting a NFS4 share in a loop: # for i in `seq 1 100`; do mount /mnt/rhel4; umount /mnt/rhel4; done ...after this, the size-8192 slab gains ~100 more active objects. I'll have to ponder how we can best track down what's actually doing these kmallocs. Maybe a systemtap script that traps on kmalloc and does a dump_stack for any that are >4096 and <8192 ?
Created attachment 294150 [details] stap script for looking at size 8192 kmallocs and their corresponding kfrees Systemtap script to try and track this down...
Created attachment 294151 [details] output from stap script Output from stap script. It looks like we have 6 kmallocs and 5 kfrees. The lingering kmalloc seems to be the second one that returned 0xffff8800025b8000. Stack trace from print_backtrace is: size = 4120, addr = 0xffff8800025b8000 Returning from: 0xffffffff802c9899 : __kmalloc+0x0/0x9f [] Returning to : 0xffffffff802bd91a : __kzalloc+0x9/0x21 [] 0xffffffff802774b8 : kretprobe_trampoline_holder+0x0/0x2 [] 0xffffffff80404f07 : reqsk_queue_alloc+0x21/0x99 [] 0xffffffff8042bc7b : inet_csk_listen_start+0x1a/0x135 [] 0xffffffff8043c59b : inet_listen+0x42/0x68 [] 0xffffffff881e2464 : svc_makesock+0x127/0x183 [sunrpc] 0xffffffff881e18b7 : svc_create+0xee/0xf8 [sunrpc] 0xffffffff883711bf : nfs_callback_up+0x9c/0x14d [nfs] 0xffffffff8834fe2f : nfs_get_client+0xfd/0x3df [nfs] 0xffffffff88350158 : nfs4_set_client+0x47/0x173 [nfs] 0xffffffff88350909 : nfs4_create_server+0x7a/0x393 [nfs] 0xffffffff8025e823 : error_exit+0x0/0x6e [] 0xffffffff883573b4 : nfs_copy_user_string+0x3c/0x89 [nfs] 0xffffffff88357cdc : nfs4_get_sb+0x1fc/0x323 [nfs] 0xffffffff8020adff : get_page_from_freelist+0x32e/0x3bc [] 0xffffffff802cee21 : vfs_kern_mount+0x93/0x11a [] 0xffffffff802ceeea : do_kern_mount+0x36/0x4d [] 0xffffffff802d855b : do_mount+0x68c/0x6fc [] 0xffffffff80418c8b : __qdisc_run+0x36/0x1bb [] 0xffffffff8022bf6b : local_bh_enable+0x9/0xa5 [] 0xffffffff80230ebb : dev_queue_xmit+0x2f2/0x313 [] 0xffffffff80233001 : ip_output+0x29a/0x2dd [] 0xffffffff802628b1 : _spin_lock_irqsave+0x9/0x14 [] 0xffffffff802229d4 : __up_read+0x19/0x7f [] 0xffffffff802d72eb : copy_mount_options+0xce/0x127 [] 0xffffffff80297b70 : search_exception_tables+0x1d/0x2d [] 0xffffffff802654f6 : do_page_fault+0x10e7/0x12cc [] 0xffffffff80263786 : do_debug+0x70/0x151 [] 0xffffffff8020b663 : kfree+0x0/0xc5 [] 0xffffffff80263f9d : kprobe_handler+0x1ac/0x1c8 [] 0xffffffff80263ff4 : kprobe_exceptions_notify+0x3b/0x75 [] 0xffffffff802656fb : notifier_call_chain+0x20/0x32 [] 0xffffffff8020acc5 : get_page_from_freelist+0x1f4/0x3bc [] 0xffffffff8020f2d0 : __alloc_pages+0x65/0x2ce [] 0xffffffff8024c3cf : sys_mount+0x8a/0xcd [] 0xffffffff8025e2f1 : tracesys+0xa7/0xb2 [] I think there's a lot of garbage in there though, but that gives me some idea of where to look...
It looks like we're calling svc_setup_socket to create a socket for the nfs4 callback thread, but I don't see where that gets torn down. I suspect that's where the problem is, but need to look a bit more closely.
The problem seems to be with the sv_nrthreads count for the callback thread. It's at 2 when we do the umount: RPC: svc_destroy(NFSv4 callback, 2) ...so it doesn't actually tear down the socket or the svc_serv. nfsd and lockd also use those functions and when they go down their refcounts seem to be OK...
This appears to be an upstream bug too. On a rawhide machine after mounting and unmounting: svc: svc_destroy(NFSv4 callback, 2) ...and I don't see where the socket got torn down. I think I see the problem, svc_create starts the service with sv_nrthreads==1. Then, svc_create_thread increments that count. nfs_callback_up() isn't handling this correctly. It should be calling svc_destroy() on success and failure, but it isn't. As an example, lockd_up_proto() handles this correctly. I'll post a patch here soon that I can propose upstream to fix this.
Created attachment 294563 [details] patch -- fix reference counting for NFS4 callback thread This patch seems to fix the problem on rawhide. Backporting to RHEL5 and RHEL4 should be trivial. I'm assuming RHEL4 has this problem too, though I need to check. I'll clone this BZ if so.
Patch posted upstream. Awaiting comment...
Looks like Trond applied the patch, so I'll plan to propose a similar one for RHEL5. It's a bit too late for RHEL5.2, but I'll try to make sure we get something for 5.3. I'll also plan to take this patch into my test kernels for you to test. Once I do, I'll post a note here so that you can test them.
Created attachment 295296 [details] patch -- flush signals before taking down callback thread Peter noticed that this seems to expose another problem with the callback thread. It doesn't flush signals on shutdown and that makes the portmap unregistration fail and throw an error. This patch seems to fix it, but he's currently chasing an NFS related deadlock and I'd like to understand that before I send this upstream.
Created attachment 302874 [details] unified patch Patch that incorporates both patches that went upstream.
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
in kernel-2.6.18-98.el5 You can download this test kernel from http://people.redhat.com/dzickus/el5
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