Re: [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN
From: John Hubbard
Date: Tue Dec 24 2019 - 21:06:57 EST
On 12/22/19 5:23 AM, Leon Romanovsky wrote:
On Fri, Dec 20, 2019 at 03:54:55PM -0800, John Hubbard wrote:
On 12/20/19 10:29 AM, Leon Romanovsky wrote:
...
$ ./build.sh
$ build/bin/run_tests.py
If you get things that far I think Leon can get a reproduction for you
I'm not so optimistic about that.
OK, I'm going to proceed for now on the assumption that I've got an overflow
problem that happens when huge pages are pinned. If I can get more information,
great, otherwise it's probably enough.
One thing: for your repro, if you know the huge page size, and the system
page size for that case, that would really help. Also the number of pins per
page, more or less, that you'd expect. Because Jason says that only 2M huge
pages are used...
Because the other possibility is that the refcount really is going negative,
likely due to a mismatched pin/unpin somehow.
If there's not an obvious repro case available, but you do have one (is it easy
to repro, though?), then *if* you have the time, I could point you to a github
branch that reduces GUP_PIN_COUNTING_BIAS by, say, 4x, by applying this:
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bb44c4d2ada7..8526fd03b978 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1077,7 +1077,7 @@ static inline void put_page(struct page *page)
* get_user_pages and page_mkclean and other calls that race to set up page
* table entries.
*/
-#define GUP_PIN_COUNTING_BIAS (1U << 10)
+#define GUP_PIN_COUNTING_BIAS (1U << 8)
void unpin_user_page(struct page *page);
void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
If that fails to repro, then we would be zeroing in on the root cause.
The branch is here (I just tested it and it seems healthy):
git@xxxxxxxxxx:johnhubbard/linux.git pin_user_pages_tracking_v11_with_diags
Hi,
We tested the following branch and here comes results:
Thanks for this testing run!
[root@server consume_mtts]# (master) $ grep foll_pin /proc/vmstat
nr_foll_pin_requested 0
nr_foll_pin_returned 0
Zero pinned pages!
...now I'm confused. Somehow FOLL_PIN and pin_user_pages*() calls are
not happening. And although the backtraces below show some of my new
routines (like try_grab_page), they also confirm the above: there is no
pin_user_page*() call in the stack.
In particular, it looks like ib_umem_get() is calling through to
get_user_pages*(), rather than pin_user_pages*(). I don't see how this
is possible, because the code on my screen shows ib_umem_get() calling
pin_user_pages_fast().
Any thoughts or ideas are welcome here.
However, glossing over all of that and assuming that the new
GUP_PIN_COUNTING_BIAS of 256 is applied, it's interesting that we still
see any overflow. I'm less confident now that this is a true refcount
overflow.
Also, any information that would get me closer to being able to attempt
my own reproduction of the problem are *very* welcome. :)
thanks,
--
John Hubbard
NVIDIA
[root@serer consume_mtts]# (master) $ dmesg
[ 425.221459] ------------[ cut here ]------------
[ 425.225894] WARNING: CPU: 1 PID: 6738 at mm/gup.c:61 try_grab_compound_head+0x90/0xa0
[ 425.228021] Modules linked in: mlx5_ib mlx5_core mlxfw mlx4_ib mlx4_en ptp pps_core mlx4_core bonding ip6_gre ip6_tunnel tunnel6 ip_gre gre ip_tunnel rdma_rxe ip6_udp_tunnel udp_tunnel rdma_ucm ib_uverbs ib_ipoib ib_umad ib_srp scsi_transport_srp rpcrdma ib_iser libiscsi scsi_transport_iscsi rdma_cm iw_cm ib_cm ib_core [last unloaded: mlxfw]
[ 425.235266] CPU: 1 PID: 6738 Comm: consume_mtts Tainted: G O 5.5.0-rc2+ #1
[ 425.237480] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 425.239738] RIP: 0010:try_grab_compound_head+0x90/0xa0
[ 425.241170] Code: 06 48 8d 4f 34 f0 0f b1 57 34 74 cd 85 c0 74 cf 8d 14 06 f0 0f b1 11 74 c0 eb f1 8d 14 06 f0 0f b1 11 74 b5 85 c0 75 f3 eb b5 <0f> 0b 31 c0 c3 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41
[ 425.245739] RSP: 0018:ffffc900006878a8 EFLAGS: 00010082
[ 425.247124] RAX: 0000000080000001 RBX: 00007f780488a000 RCX: 0000000000000bb0
[ 425.248956] RDX: ffffea000e031087 RSI: 0000000000008a00 RDI: ffffea000dc58000
[ 425.250761] RBP: ffffea000e031080 R08: ffffc90000687974 R09: 000fffffffe00000
[ 425.252661] R10: 0000000000000000 R11: ffff888362560000 R12: 000000000000008a
[ 425.254487] R13: 80000003716000e7 R14: 00007f780488a000 R15: ffffc90000687974
[ 425.256309] FS: 00007f780d9d3740(0000) GS:ffff8883b1c80000(0000) knlGS:0000000000000000
[ 425.258401] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 425.259949] CR2: 0000000002334048 CR3: 000000039c68c001 CR4: 00000000001606a0
[ 425.261884] Call Trace:
[ 425.262735] gup_pgd_range+0x517/0x5a0
[ 425.263819] internal_get_user_pages_fast+0x210/0x250
[ 425.265193] ib_umem_get+0x298/0x550 [ib_uverbs]
[ 425.266476] mr_umem_get+0xc9/0x260 [mlx5_ib]
[ 425.267699] mlx5_ib_reg_user_mr+0xcc/0x7e0 [mlx5_ib]
[ 425.269134] ? xas_load+0x8/0x80
[ 425.270074] ? xa_load+0x48/0x90
[ 425.271038] ? lookup_get_idr_uobject.part.10+0x12/0x70 [ib_uverbs]
[ 425.272757] ib_uverbs_reg_mr+0x127/0x280 [ib_uverbs]
[ 425.274120] ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xc2/0xf0 [ib_uverbs]
[ 425.276058] ib_uverbs_cmd_verbs.isra.6+0x5be/0xbe0 [ib_uverbs]
[ 425.277657] ? uverbs_disassociate_api+0xd0/0xd0 [ib_uverbs]
[ 425.279155] ? __alloc_pages_nodemask+0x148/0x2b0
[ 425.280445] ib_uverbs_ioctl+0xc0/0x120 [ib_uverbs]
[ 425.281755] do_vfs_ioctl+0x9d/0x650
[ 425.282766] ksys_ioctl+0x70/0x80
[ 425.283745] __x64_sys_ioctl+0x16/0x20
[ 425.284912] do_syscall_64+0x42/0x130
[ 425.285973] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 425.287377] RIP: 0033:0x7f780d2df267
[ 425.288449] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
[ 425.293073] RSP: 002b:00007ffce49a88a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 425.295034] RAX: ffffffffffffffda RBX: 00007ffce49a8938 RCX: 00007f780d2df267
[ 425.296895] RDX: 00007ffce49a8920 RSI: 00000000c0181b01 RDI: 0000000000000003
[ 425.298689] RBP: 00007ffce49a8900 R08: 0000000000000003 R09: 00007f780d9a1010
[ 425.300480] R10: 00000000ffffffff R11: 0000000000000246 R12: 00007f780d9a1150
[ 425.302290] R13: 00007ffce49a8900 R14: 00007ffce49a8ad8 R15: 00007f780468a000
[ 425.304113] ---[ end trace 1ecbefdb403190dd ]---
[ 425.305434] ------------[ cut here ]------------
[ 425.307147] WARNING: CPU: 1 PID: 6738 at mm/gup.c:150 try_grab_page+0x56/0x60
[ 425.309111] Modules linked in: mlx5_ib mlx5_core mlxfw mlx4_ib mlx4_en ptp pps_core mlx4_core bonding ip6_gre ip6_tunnel tunnel6 ip_gre gre ip_tunnel rdma_rxe ip6_udp_tunnel udp_tunnel rdma_ucm ib_uverbs ib_ipoib ib_umad ib_srp scsi_transport_srp rpcrdma ib_iser libiscsi scsi_transport_iscsi rdma_cm iw_cm ib_cm ib_core [last unloaded: mlxfw]
[ 425.316461] CPU: 1 PID: 6738 Comm: consume_mtts Tainted: G W O 5.5.0-rc2+ #1
[ 425.318582] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 425.320958] RIP: 0010:try_grab_page+0x56/0x60
[ 425.322167] Code: 7e 28 f0 81 47 34 00 01 00 00 c3 48 8b 47 08 48 8d 50 ff a8 01 48 0f 45 fa 8b 47 34 85 c0 7e 0f f0 ff 47 34 b8 01 00 00 00 c3 <0f> 0b 31 c0 c3 0f 0b 31 c0 c3 0f 1f 44 00 00 41 57 41 56 41 55 41
[ 425.326814] RSP: 0018:ffffc90000687830 EFLAGS: 00010282
[ 425.328226] RAX: 0000000000000001 RBX: ffffea000dc58000 RCX: ffffea000e031087
[ 425.330104] RDX: 0000000080000001 RSI: 0000000000040000 RDI: ffffea000dc58000
[ 425.331980] RBP: 00007f7804800000 R08: 000ffffffffff000 R09: 80000003716000e7
[ 425.333898] R10: ffff88834af80120 R11: ffff8883ac16f000 R12: ffff88834af80120
[ 425.335704] R13: ffff88837c0915c0 R14: 0000000000050201 R15: 00007f7804800000
[ 425.337638] FS: 00007f780d9d3740(0000) GS:ffff8883b1c80000(0000) knlGS:0000000000000000
[ 425.339734] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 425.341369] CR2: 0000000002334048 CR3: 000000039c68c001 CR4: 00000000001606a0
[ 425.343160] Call Trace:
[ 425.343967] follow_trans_huge_pmd+0x16f/0x2e0
[ 425.345263] follow_p4d_mask+0x51c/0x630
[ 425.346344] __get_user_pages+0x1a1/0x6c0
[ 425.347463] internal_get_user_pages_fast+0x17b/0x250
[ 425.348918] ib_umem_get+0x298/0x550 [ib_uverbs]
[ 425.350174] mr_umem_get+0xc9/0x260 [mlx5_ib]
[ 425.351383] mlx5_ib_reg_user_mr+0xcc/0x7e0 [mlx5_ib]
[ 425.352849] ? xas_load+0x8/0x80
[ 425.353776] ? xa_load+0x48/0x90
[ 425.354730] ? lookup_get_idr_uobject.part.10+0x12/0x70 [ib_uverbs]
[ 425.356410] ib_uverbs_reg_mr+0x127/0x280 [ib_uverbs]
[ 425.357843] ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xc2/0xf0 [ib_uverbs]
[ 425.359749] ib_uverbs_cmd_verbs.isra.6+0x5be/0xbe0 [ib_uverbs]
[ 425.361405] ? uverbs_disassociate_api+0xd0/0xd0 [ib_uverbs]
[ 425.362898] ? __alloc_pages_nodemask+0x148/0x2b0
[ 425.364206] ib_uverbs_ioctl+0xc0/0x120 [ib_uverbs]
[ 425.365564] do_vfs_ioctl+0x9d/0x650
[ 425.366567] ksys_ioctl+0x70/0x80
[ 425.367537] __x64_sys_ioctl+0x16/0x20
[ 425.368698] do_syscall_64+0x42/0x130
[ 425.369782] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 425.371117] RIP: 0033:0x7f780d2df267
[ 425.372159] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
[ 425.376774] RSP: 002b:00007ffce49a88a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 425.378740] RAX: ffffffffffffffda RBX: 00007ffce49a8938 RCX: 00007f780d2df267
[ 425.380598] RDX: 00007ffce49a8920 RSI: 00000000c0181b01 RDI: 0000000000000003
[ 425.382411] RBP: 00007ffce49a8900 R08: 0000000000000003 R09: 00007f780d9a1010
[ 425.384312] R10: 00000000ffffffff R11: 0000000000000246 R12: 00007f780d9a1150
[ 425.386132] R13: 00007ffce49a8900 R14: 00007ffce49a8ad8 R15: 00007f780468a000
[ 425.387964] ---[ end trace 1ecbefdb403190de ]---
Thanks
thanks,
--
John Hubbard
NVIDIA