Rick Macklem wrote: >r358098 will hang fairly easily, in 1-3 cycles of the kernel build over NFS. >I thought this was the culprit, since I did 6 cycles of r358097 without a hang. >However, I just got a hang with r358097, but it looks rather different. >The r358097 hang did not have any processes sleeping on btalloc. They >appeared to be waiting on two different locks in the buffer cache. >As such, I think it might be a different problem. (I'll admit I should have >made notes about this one before rebooting, but I was flustrated that >it happened and rebooted before looking at it mush detail.) Ok, so I did 10 cycles of the kernel build over NFS for r358096 and never got a hang. --> It seems that r358097 is the culprit and r358098 makes it easier to reproduce. --> Basically runs out of kernel memory. It is not obvious if I can revert these two commits without reverting other ones, since there were a bunch of vm changes after these. I'll take a look, but if you guys have any ideas on how to fix this, please let me know. Thanks, rick Jeff, to fill you in, I have been getting intermittent hangs on a Pentium 4 (single core i386) with 1.25Gbytes ram when doing kernel builds using head kernels from this winter. (I also saw one when doing a kernel build on UFS, so they aren't NFS specific, although easier to reproduce that way.) After a typical hang, there will be a bunch of processes sleeping on "btalloc" and several processes holding the following lock: exclusive sx lock _at_ vm/vm_map.c:4761 - I have seen hangs where that is the only lock held by any process except the interrupt thread. - I have also seen processes waiting on the following locks: kern/subr_vmem.c:1343 kern/subr_vmem.c:633 I can't be absolutely sure r358098 is the culprit, but it seems to make the problem more reproducible. If anyone has a patch suggestion, I can test it. Otherwise, I will continue to test r358097 and earlier, to try and see what hangs occur. (I've done 8 cycles of testing of r356776 without difficulties, but that doesn't guarantee it isn't broken.) There is a bunch more of the stuff I got for Kostik and Ryan below. I can do "db" when it is hung, but it is a screen console, so I need to transcribe the output to email by hand. (ie. If you need something specific I can do that, but trying to do everything Kostik and Ryan asked for isn't easy.) rick Konstantin Belousov wrote: >On Fri, May 22, 2020 at 11:46:26PM +0000, Rick Macklem wrote: >> Konstantin Belousov wrote: >> >On Wed, May 20, 2020 at 11:58:50PM -0700, Ryan Libby wrote: >> >> On Wed, May 20, 2020 at 6:04 PM Rick Macklem <rmacklem_at_uoguelph.ca> wrote: >> >> > >> >> > Hi, >> >> > >> >> > Since I hadn't upgraded a kernel through the winter, it took me a while >> >> > to bisect this, but r358252 seems to be the culprit. No longer true. I succeeded in reproducing the hang to-day running a r358251 kernel. I haven't had much luck sofar, but see below for what I have learned. >> >> > >> >> > If I do a kernel build over NFS using my not so big Pentium 4 (single core, >> >> > 1.25Gbytes RAM, i386), about every second attempt will hang. >> >> > When I do a "ps" in the debugger, I see processes sleeping on btalloc. >> >> > If I revert to r358251, I cannot reproduce this. As above, this is no longer true. >> >> > >> >> > Any ideas? >> >> > >> >> > I can easily test any change you might suggest to see if it fixes the >> >> > problem. >> >> > >> >> > If you want more debug info, let me know, since I can easily >> >> > reproduce it. >> >> > >> >> > Thanks, rick >> >> >> >> Nothing obvious to me. I can maybe try a repro on a VM... >> >> >> >> ddb ps, acttrace, alltrace, show all vmem, show page would be welcome. >> >> >> >> "btalloc" is "We're either out of address space or lost a fill race." >From what I see, I think it is "out of address space". For one of the hangs, when I did "show alllocks", everything except the intr thread, was waiting for the exclusive sx lock _at_ vm/vm_map.c:4761 >> > >> >Yes, I would be not surprised to be out of something on 1G i386 machine. >> >Please also add 'show alllocks'. >> Ok, I used an up to date head kernel and it took longer to reproduce a hang. Go down to Kostik's comment about kern.maxvnodes for the rest of what I've learned. (The time it takes to reproduce one of these varies greatly, but I usually get one within 3 cycles of a full kernel build over NFS. I have had it happen once when doing a kernel build over UFS.) >> This time, none of the processes are stuck on "btalloc". > I'll try and give you most of the above, but since I have to type it in by hand > from the screen, I might not get it all. (I'm no real typist;-) > > show alllocks > exclusive lockmgr ufs (ufs) r = 0 locked _at_ kern/vfs_subr.c: 3259 > exclusive lockmgr nfs (nfs) r = 0 locked _at_ kern/vfs_lookup.c:737 > exclusive sleep mutex kernel area domain (kernel arena domain) r = 0 locked _at_ kern/subr_vmem.c:1343 > exclusive lockmgr bufwait (bufwait) r = 0 locked _at_ kern/vfs_bio.c:1663 > exclusive lockmgr ufs (ufs) r = 0 locked _at_ kern/vfs_subr.c:2930 > exclusive lockmgr syncer (syncer) r = 0 locked _at_ kern/vfs_subr.c:2474 > Process 12 (intr) thread 0x.. (1000008) > exclusive sleep mutex Giant (Giant) r = 0 locked _at_ kern/kern_intr.c:1152 > > > ps > - Not going to list them all, but here are the ones that seem interesting... > 18 0 0 0 DL vlruwt 0x11d939cc [vnlru] > 16 0 0 0 DL (threaded) [bufdaemon] > 100069 D qsleep [bufdaemon] > 100074 D - [bufspacedaemon-0] > 100084 D sdflush 0x11923284 [/ worker] > - and more of these for the other UFS file systems > 9 0 0 0 DL psleep 0x1e2f830 [vmdaemon] > 8 0 0 0 DL (threaded) [pagedaemon] > 100067 D psleep 0x1e2e95c [dom0] > 100072 D launds 0x1e2e968 [laundry: dom0] > 100073 D umarcl 0x12cc720 [uma] > … a bunch of usb and cam ones > 100025 D - 0x1b2ee40 [doneq0] > … > 12 0 0 0 RL (threaded) [intr] > 100007 I [swi6: task queue] > 100008 Run CPU 0 [swi6: Giant taskq] > … > 100000 D swapin 0x1d96dfc [swapper] > - and a bunch more in D state. > Does this mean the swapper was trying to swap in? > > > acttrace > - just shows the keyboard > kdb_enter() at kdb_enter+0x35/frame > vt_kbdevent() at vt_kdbevent+0x329/frame > kdbmux_intr() at kbdmux_intr+0x19/frame > taskqueue_run_locked() at taskqueue_run_locked+0x175/frame > taskqueue_run() at taskqueue_run+0x44/frame > taskqueue_swi_giant_run(0) at taskqueue_swi_giant_run+0xe/frame > ithread_loop() at ithread_loop+0x237/frame > fork_exit() at fork_exit+0x6c/frame > fork_trampoline() at 0x../frame > > > show all vmem > vmem 0x.. 'transient arena' > quantum: 4096 > size: 23592960 > inuse: 0 > free: 23592960 > busy tags: 0 > free tags: 2 > inuse size free size > 16777216 0 0 1 23592960 > vmem 0x.. 'buffer arena' > quantum: 4096 > size: 94683136 > inuse: 94502912 > free: 180224 > busy tags: 1463 > free tags: 3 > inuse size free size > 16384 2 32768 1 16384 > 32768 39 1277952 1 32768 > 65536 1422 93192192 0 0 > 131072 0 0 1 131072 > vmem 0x.. 'i386trampoline' > quantum: 1 > size: 24576 > inuse: 20860 > free: 3716 > busy tags: 9 > free tags: 3 > inuse size free size > 32 1 48 1 52 > 64 2 208 0 0 > 128 2 280 0 0 > 2048 1 2048 1 3664 > 4096 2 8192 0 0 > 8192 1 10084 0 0 > vmem 0x.. 'kernel rwx arena' > quantum: 4096 > size: 0 > inuse: 0 > free: 0 > busy tags: 0 > free tags: 0 > vmem 0x.. 'kernel area dom' > quantum: 4096 > size: 56623104 > inuse: 56582144 >> free: 40960 >> busy tags: 11224 >> free tags: 3 >I think this is the trouble. > >Did you tried to reduce kern.maxvnodes ? What is the default value for >the knob on your machine ? The default is 84342. I have tried 64K, 32K and 128K and they all hung sooner or later. For the 32K case, I did see vnodes being recycled for a while before it got hung, so it isn't just when it hits the limit. Although it is much easier for me to reproduce on an NFS mount, I did see a hang while doing a kernel build on UFS (no NFS mount on the machine at that time). So, I now know that the problem pre-dates r358252 and is not NFS specific. I'm not bisecting back further to try and isolate the commit that causes this. (Unfortunately, each test cycle can take days. I now know that I have to do several of these kernel builds, which take hours each, to see if a hang is going to happen.) I'll post if/when I have more, rick We scaled maxvnodes for ZFS and UFS, might be NFS is even more demanding, having larger node size. > inuse size free size > 4096 11091 45428736 0 0 > 8192 63 516096 0 0 > 16384 12 196608 0 0 > 32768 6 196608 0 0 > 40960 2 81920 1 40960 > 65536 16 1048576 0 0 > 94208 1 94208 0 0 > 110592 1 110592 0 0 > 131072 15 2441216 0 0 > 262144 15 3997696 0 0 > 524288 1 524288 0 0 > 1048576 1 1945600 0 0 > vmem 0x.. 'kernel arena' > quantum: 4096 > size: 390070272 > inuse: 386613248 > free: 3457024 > busy tags: 873 > free tags: 3 > inuse size free size > 4096 35 143360 1 4096 > 8192 2 16384 2 16384 > 12288 1 12288 0 0 > 16384 30 491520 0 0 > 20480 140 2867200 0 0 > 65536 1 65536 0 0 > 131072 631 82706432 0 0 > 1048576 0 0 1 1339392 > 2097152 27 56623104 1 2097152 > 8388608 1 13774848 0 0 > 16777216 3 74883072 0 0 > 33554432 1 36753408 0 0 > 67108864 1 118276096 0 0 > > > alltrace > - I can't face typing too much more, but I'll put a few > here that look interesting > > - for csh > sched_switch() > mi_switch() > kern_yield() > getblkx() > breadn_flags() > ffs_update() > ufs_inactive() > VOP_INACTIVE() > vinactivef() > vput_final() > vm_object_deallocate() > vm_map_process_deferred() > kern_munmap() > sys_munmap() > > - For cc > sched_switch() > mi_switch() > sleepq_switch() > sleepq_timedwait() > _sleep() > pause_sbt() > vmem_bt_alloc() > keg_alloc_slab() > zone_import() > cache_alloc() > cache_alloc_retry() > uma_zalloc_arg() > bt_fill() > vmem_xalloc() > vmem_alloc() > kmem_alloc() > kmem_malloc_domainset() > page_alloc() > keg_alloc_slab() > zone_import() > cache_alloc() > cache_alloc_retry() > uma_zalloc_arg() > nfscl_nget() > nfs_create() > vop_sigdefer() > nfs_vnodeops_bypass() > VOP_CREATE_APV() > vn_open_cred() > vn_open() > kern_openat() > sys_openat() > > Then there are a bunch of these... for cc, make > sched_switch() > mi_switch() > sleepq_switch() > sleepq_catch_signals() > sleepq_wait_sig() > kern_wait6() > sys_wait4() > > - for vnlru > sched_switch() > mi_switch() > sleepq_switch() > sleepq_timedwait() > _sleep() > vnlru_proc() > fork_exit() > fork_trampoline() > > - for syncer > sched_switch() > mi_switch() > critical_exit_preempt() > intr_event_handle() > intr_execute_handlers() > lapic_handle_intr() > Xapic_isr1() > - interrupt > memset() > cache_alloc() > cache_alloc_retry() > uma_zalloc_arg() > vmem_xalloc() > vmem_bt_alloc() > keg_alloc_slab() > zone_import() > cache_alloc() > cache_alloc_retry() > uma_zalloc_arg() > bt_fill() > vmem_xalloc() > vmem_alloc() > bufkva_alloc() > getnewbuf() > getblkx() > breadn_flags() > ffs_update() > ffs_sync() > sync_fsync() > VOP_FSYNC_APV() > sched_sync() > fork_exit() > fork_trampoline() > > - For bufdaemon (a bunch of these) > sched_switch() > mi_switch() > sleepq_switch() > sleepq_timedwait() > _sleep() > buf_daemon() > fork_exit() > fork_trampoline() > > vmdaemon and pagedaemon are basically just like above, > sleeping in > vm_daemon() > or > vm_pageout_worker() > or > vm_pageout_laundry_worker() > or > uma_reclaim_worker() > > That's all the typing I can take right now. > I can probably make this happen again if you want more specific stuff. > > rick > > > > _______________________________________________ freebsd-current_at_freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" _______________________________________________ freebsd-current_at_freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" _______________________________________________ freebsd-current_at_freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"Received on Mon Jun 15 2020 - 22:06:44 UTC
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