Large kmem_alloc(131072, 0x1000)

[dpavlin]

When trying to create ext4 filesystem on zvol i got following in my dmesg:

[  217.493487] Large kmem_alloc(131072, 0x1000), please file an issue at:
               https://github.com/zfsonlinux/zfs/issues/new
[  217.493493] CPU: 3 PID: 8595 Comm: zvol Tainted: P           O    4.0.0-2-amd64 #1 Debian 4.0.8-1
[  217.493494] Hardware name: Dell Inc. Precision T3610/09M8Y8, BIOS A06 02/28/2014
[  217.493496]  0000000000000000 0000000000000000 ffffffff81562ce2 000000000000c210
[  217.493499]  ffffffffa0629cb2 ffffffffa09c7b63 ffff880076ed3858 0000000000004000
[  217.493500]  0000000000000000 ffffffffa09c7b63 000000078c000000 0000000000000000
[  217.493502] Call Trace:
[  217.493510]  [<ffffffff81562ce2>] ? dump_stack+0x40/0x50
[  217.493526]  [<ffffffffa0629cb2>] ? spl_kmem_zalloc+0x152/0x1d0 [spl]
[  217.493539]  [<ffffffffa091b079>] ? dmu_buf_hold_array_by_dnode+0x99/0x500 [zfs]
[  217.493547]  [<ffffffffa091b5bc>] ? dmu_buf_hold_array+0x5c/0x80 [zfs]
[  217.493555]  [<ffffffffa091c916>] ? dmu_write_req+0x66/0x1d0 [zfs]
[  217.493564]  [<ffffffffa09be96a>] ? zvol_write+0x10a/0x470 [zfs]
[  217.493578]  [<ffffffff81564190>] ? __schedule+0x2a0/0x920
[  217.493582]  [<ffffffffa062d2b6>] ? taskq_thread+0x1f6/0x440 [spl]
[  217.493586]  [<ffffffff81097570>] ? wake_up_state+0x20/0x20
[  217.493590]  [<ffffffffa062d0c0>] ? taskq_cancel_id+0x110/0x110 [spl]
[  217.493592]  [<ffffffff8108ab41>] ? kthread+0xc1/0xe0
[  217.493594]  [<ffffffff8108aa80>] ? kthread_create_on_node+0x180/0x180
[  217.493596]  [<ffffffff81568dd8>] ? ret_from_fork+0x58/0x90
[  217.493598]  [<ffffffff8108aa80>] ? kthread_create_on_node+0x180/0x180
[  217.494954] Large kmem_alloc(131072, 0x1000), please file an issue at:
               https://github.com/zfsonlinux/zfs/issues/new
[  217.494959] CPU: 2 PID: 8591 Comm: zvol Tainted: P           O    4.0.0-2-amd64 #1 Debian 4.0.8-1
[  217.494960] Hardware name: Dell Inc. Precision T3610/09M8Y8, BIOS A06 02/28/2014
[  217.494961]  0000000000000000 0000000000000000 ffffffff81562ce2 000000000000c210
[  217.494963]  ffffffffa0629cb2 ffffffffa09c7b63 ffff880076ed3858 0000000000004000
[  217.494965]  0000000000000000 ffffffffa09c7b63 0000000788000000 0000000000000000
[  217.494966] Call Trace:
[  217.494971]  [<ffffffff81562ce2>] ? dump_stack+0x40/0x50
[  217.494979]  [<ffffffffa0629cb2>] ? spl_kmem_zalloc+0x152/0x1d0 [spl]
[  217.494989]  [<ffffffffa091b079>] ? dmu_buf_hold_array_by_dnode+0x99/0x500 [zfs]
[  217.494997]  [<ffffffffa091b5bc>] ? dmu_buf_hold_array+0x5c/0x80 [zfs]
[  217.495005]  [<ffffffffa091c916>] ? dmu_write_req+0x66/0x1d0 [zfs]
[  217.495013]  [<ffffffffa09be96a>] ? zvol_write+0x10a/0x470 [zfs]
[  217.495015]  [<ffffffff81564190>] ? __schedule+0x2a0/0x920
[  217.495019]  [<ffffffffa062d2b6>] ? taskq_thread+0x1f6/0x440 [spl]
[  217.495022]  [<ffffffff81097570>] ? wake_up_state+0x20/0x20
[  217.495025]  [<ffffffffa062d0c0>] ? taskq_cancel_id+0x110/0x110 [spl]
[  217.495027]  [<ffffffff8108ab41>] ? kthread+0xc1/0xe0
[  217.495029]  [<ffffffff8108aa80>] ? kthread_create_on_node+0x180/0x180
[  217.495031]  [<ffffffff81568dd8>] ? ret_from_fork+0x58/0x90
[  217.495033]  [<ffffffff8108aa80>] ? kthread_create_on_node+0x180/0x180

This is using latest Debian packages, 0.6.4-21-53b1d9-wheezy

[behlendorf]

@dpavlin the warning is just advisory but it still needs to be explained. Have you made any non-default tunings to the zvol? For example, what's the record size set too? In the meanwhile you can suppress the warning by increasing the default warning threshold which is safe.

echo $((256*1024)) >/sys/module/spl/parameters/spl_kmem_alloc_warn

[dpavlin]

I'm creating filesystem with

zfs create -V 60G -b 4k -s klinz/block/blabla

However, I'm not getting warning in dmesg after that command, but instead after

mkfs.ext4 -m 0 -L blabla /dev/zvol/klinz/block/blabla

I also noticed that mkfs.ext4 does finish and create file-system, but label never appears in /dev/disk/by-label/. I'm not sure if this is zfs related or not, but it did work correctly with last zfs Debian package revision. Kernel used is Linux klin 4.0.0-2-amd64 #1 SMP Debian 4.0.8-1 (2015-07-11) x86_64 GNU/Linux from Debian sid. I don't think I updated it since it worked list time, and even if I did it was some version, but newer build.

I have script which waits for label of new file-system to appear, so this is somewhat a show-stopper for me.

With sparse and default volblocksize of 8K i'm getting also warning for for smaller allocation: Large kmem_alloc(65536, 0x1000) and same backtrace.

Removing sparse option to zfs create doesn't change warnings.

[dpavlin]

I tried similar test on Linux mlin 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1 (2015-05-24) x86_64 GNU/Linux on Debian jessie (current stable) and I'm not seeing any warnings in dmesg nor problems with labels. So it seems that it's a kernel problem (perhaps) and not zfsonlinux one. Feel free to close this issue if you agree with this.

[prometheanfire]

should this be combined with #3684

[behlendorf]

@prometheanfire yes, yes it should. Thanks for noticing this one, this is a duplicate of #3684 and was resolved by commit c495fe2.