Re: [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit policy

From: Qian Cai
Date: Thu May 28 2020 - 10:18:15 EST

On Wed, May 27, 2020 at 06:46:06PM +0800, Feng Tang wrote:
> Hi Qian,
>
> On Tue, May 26, 2020 at 10:25:39PM -0400, Qian Cai wrote:
> > > > > > [1] https://lkml.org/lkml/2020/3/5/57
> > > > >
> > > > > Reverted this series fixed a warning under memory pressue.
> > > >
> > > > Andrew, Stephen, can you drop this series?
> > > >
> > > > >
> > > > > [ 3319.257898] LTP: starting oom01
> > > > > [ 3319.284417] ------------[ cut here ]------------
> > > > > [ 3319.284439] memory commitment underflow
> > >
> > > Thanks for the catch!
> > >
> > > Could you share the info about the platform, like the CPU numbers
> > > and RAM size, and what's the mmap test size of your test program.
> > > It would be great if you can point me the link to the test program.
> >
> > I have been reproduced this on both AMD and Intel. The test just
> > allocating memory and swapping.
> >
> > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/oom/oom01.c
> > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/tunable/overcommit_memory.c
> >
> > It might be better to run the whole LTP mm tests if none of the above
> > triggers it for you which has quite a few memory pressurers.
> >
> > /opt/ltp/runltp -f mm
>
> Thanks for sharing. I tried to reproduce this on 2 server plaforms,
> but can't reproduce it, and they are still under testing.
>
> Meanwhile, could you help to try the below patch, which is based on
> Andi's suggestion and have some debug info. The warning is a little
> strange, as the condition is
>
> (percpu_counter_read(&vm_committed_as) <
> -(s64)vm_committed_as_batch * num_online_cpus())
>
> while for your platform (48 CPU + 128 GB RAM), the
> '-(s64)vm_committed_as_batch * num_online_cpus()'
> is a s64 value: '-32G', which makes the condition hard to be true,
> and when it is, it could be triggered by some magic for s32/s64
> operations around the percpu-counter.

The patch below does not fix anything.

[ 3160.275230][ T7955] LTP: starting oom01
[ 3160.306977][T106365] KK as:-59683 as_sum:6896 check:-32768 batch:256
[ 3160.307161][T106365] ------------[ cut here ]------------
[ 3160.307184][T106365] memory commitment underflow
[ 3160.307216][T106365] WARNING: CPU: 103 PID: 106365 at mm/util.c:858 __vm_enough_memory+0x204/0x250
[ 3160.307275][T106365] Modules linked in: brd ext4 crc16 mbcache jbd2 loop kvm_hv kvm ip_tables x_tables xfs sd_mod bnx2x ahci libahci mdio tg3 libata libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod
[ 3160.307341][T106365] CPU: 103 PID: 106365 Comm: oom01 Not tainted 5.7.0-rc7-next-20200528+ #3
[ 3160.307368][T106365] NIP: c0000000003ee654 LR: c0000000003ee650 CTR: c000000000745b40
[ 3160.307382][T106365] REGS: c0002017f940f730 TRAP: 0700 Not tainted (5.7.0-rc7-next-20200528+)
[ 3160.307409][T106365] MSR: 900000000282b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 28222482 XER: 00000000
[ 3160.307442][T106365] CFAR: c00000000010e428 IRQMASK: 0
[ 3160.307442][T106365] GPR00: c0000000003ee650 c0002017f940f9c0 c00000000130a300 000000000000001b
[ 3160.307442][T106365] GPR04: c0000000017b8d68 0000000000000006 0000000078154885 ffffffff6ca32090
[ 3160.307442][T106365] GPR08: 0000201cc61a0000 0000000000000000 0000000000000000 0000000000000003
[ 3160.307442][T106365] GPR12: 0000000000002000 c000201fff675100 0000000000000000 0000000000000000
[ 3160.307442][T106365] GPR16: 0000000000000000 0000000000000000 c000200350fe3b60 fffffffffff7dfff
[ 3160.307442][T106365] GPR20: c000201a36824928 c000201a3682c128 c000200ee33ad3a0 c000200ee33ad3a8
[ 3160.307442][T106365] GPR24: c000200ee33ad390 ffffffffffff16dd 0000000000000000 0000000000000001
[ 3160.307442][T106365] GPR28: c000201a36824880 0000000000000001 c000000003fa2a80 c0000000011fb0a8
[ 3160.307723][T106365] NIP [c0000000003ee654] __vm_enough_memory+0x204/0x250
[ 3160.307759][T106365] LR [c0000000003ee650] __vm_enough_memory+0x200/0x250
[ 3160.307793][T106365] Call Trace:
[ 3160.307814][T106365] [c0002017f940f9c0] [c0000000003ee650] __vm_enough_memory+0x200/0x250 (unreliable)
[ 3160.307875][T106365] [c0002017f940fa60] [c000000000109ab8] dup_mm+0x2a8/0x700
[ 3160.307901][T106365] [c0002017f940fb10] [c00000000010b3f0] copy_process+0xeb0/0x1920
[ 3160.307927][T106365] [c0002017f940fc20] [c00000000010c1cc] _do_fork+0xac/0xb20
[ 3160.307941][T106365] [c0002017f940fd00] [c00000000010cdf8] __do_sys_clone+0x98/0xe0
[ 3160.307979][T106365] [c0002017f940fdc0] [c000000000038a88] system_call_exception+0x108/0x1d0
[ 3160.308018][T106365] [c0002017f940fe20] [c00000000000c9f0] system_call_common+0xf0/0x278
[ 3160.308054][T106365] Instruction dump:
[ 3160.308076][T106365] 60000000 60000000 60000000 73490001 4082fee4 3c62ff8c 39200001 3d42fff9
[ 3160.308128][T106365] 38632788 992a6b4a 4bd1fd75 60000000 <0fe00000> 4bfffec0 7fc3f378 483218f9
[ 3160.308158][T106365] irq event stamp: 760
[ 3160.308181][T106365] hardirqs last enabled at (759): [<c0000000001e9838>] vprintk_emit+0x118/0x430
[ 3160.308231][T106365] hardirqs last disabled at (760): [<c00000000000963c>] program_check_common_virt+0x2bc/0x310
[ 3160.308281][T106365] softirqs last enabled at (0): [<c00000000010ac38>] copy_process+0x6f8/0x1920
[ 3160.308297][T106365] softirqs last disabled at (0): [<0000000000000000>] 0x0
[ 3160.308310][T106365] ---[ end trace e2152aa44c190593 ]---
[ 3160.308478][T106365] KK as:-59683 as_sum:6897 check:-32768 batch:256
[ 3160.308614][T106365] KK as:-59683 as_sum:6898 check:-32768 batch:256
[ 3160.308714][T106365] KK as:-59683 as_sum:6901 check:-32768 batch:256
[ 3160.308806][T106365] KK as:-59683 as_sum:6902 check:-32768 batch:256
[ 3160.308900][T106365] KK as:-59683 as_sum:6903 check:-32768 batch:256
[ 3160.308979][T106365] KK as:-59683 as_sum:6904 check:-32768 batch:256
[ 3160.309064][T106365] KK as:-59683 as_sum:6905 check:-32768 batch:256
[ 3160.309160][T106365] KK as:-59683 as_sum:6906 check:-32768 batch:256
[ 3160.309275][T106365] KK as:-59683 as_sum:6907 check:-32768 batch:256
[ 3160.309356][T106365] KK as:-59683 as_sum:6908 check:-32768 batch:256
[ 3160.309437][T106365] KK as:-59683 as_sum:6909 check:-32768 batch:256
[ 3160.310939][T106366] KK as:-59683 as_sum:6912 check:-32768 batch:256
[ 3160.311134][T106366] KK as:-59270 as_sum:7040 check:-32768 batch:256
[ 3160.311240][T106367] KK as:-59270 as_sum:7168 check:-32768 batch:256

>
> Thanks,
> Feng
>
> ---
> mm/util.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 988d11e6c17c..2f3a2e0f12ae 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -797,10 +797,15 @@ EXPORT_SYMBOL_GPL(vm_memory_committed);
> int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> {
> long allowed;
> -
> - VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
> + if (percpu_counter_read(&vm_committed_as) <
> + -(s64)vm_committed_as_batch * num_online_cpus()) {
> + printk("as:%lld as_sum:%lld check:%lld batch:%d\n",
> + percpu_counter_read(&vm_committed_as),
> + percpu_counter_sum(&vm_committed_as),
> -(s64)vm_committed_as_batch * num_online_cpus(),
> - "memory commitment underflow");
> + vm_committed_as_batch);
> +
> + }
>
> vm_acct_memory(pages);
>
> @@ -816,6 +821,10 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> return 0;
> }
>
> + VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
> + -(s64)vm_committed_as_batch * num_online_cpus(),
> + "memory commitment underflow");
> +
> allowed = vm_commit_limit();
> /*
> * Reserve some for root
> --
> 2.14.1
>
> >
> > # lscpu
> > Architecture: x86_64
> > CPU op-mode(s): 32-bit, 64-bit
> > Byte Order: Little Endian
> > CPU(s): 48
> > On-line CPU(s) list: 0-47
> > Thread(s) per core: 1
> > Core(s) per socket: 12
> > Socket(s): 4
> > NUMA node(s): 4
> > Vendor ID: GenuineIntel
> > CPU family: 6
> > Model: 63
> > Model name: Intel(R) Xeon(R) CPU E5-4650 v3 @ 2.10GHz
> > Stepping: 2
> > CPU MHz: 1198.498
> > BogoMIPS: 4195.14
> > Virtualization: VT-x
> > L1d cache: 32K
> > L1i cache: 32K
> > L2 cache: 256K
> > L3 cache: 30720K
> > NUMA node0 CPU(s): 0-5,24-29
> > NUMA node1 CPU(s): 6-11,30-35
> > NUMA node2 CPU(s): 12-17,36-41
> > NUMA node3 CPU(s): 18-23,42-47
> >
> > # numactl -H
> > available: 4 nodes (0-3)
> > node 0 cpus: 0 1 2 3 4 5 24 25 26 27 28 29
> > node 0 size: 27768 MB
> > node 0 free: 27539 MB
> > node 1 cpus: 6 7 8 9 10 11 30 31 32 33 34 35
> > node 1 size: 32225 MB
> > node 1 free: 32009 MB
> > node 2 cpus: 12 13 14 15 16 17 36 37 38 39 40 41
> > node 2 size: 32253 MB
> > node 2 free: 32174 MB
> > node 3 cpus: 18 19 20 21 22 23 42 43 44 45 46 47
> > node 3 size: 32252 MB
> > node 3 free: 31330 MB
> > node distances:
> > node 0 1 2 3
> > 0: 10 21 21 21
> > 1: 21 10 21 21
> > 2: 21 21 10 21
> > 3: 21 21 21 10
> >
> > >
> > > Thanks,
> > > Feng
> > >
> > > > > [ 3319.284456] WARNING: CPU: 13 PID: 130949 at mm/util.c:835 __vm_enough_memory+0x1dc/0x1f0
> > > > > [ 3319.284485] Modules linked in: brd ext4 crc16 mbcache jbd2 loop kvm_hv kvm ip_tables x_tables xfs sd_mod ahci libahci bnx2x libata mdio tg3 libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod
> > > > > [ 3319.284538] CPU: 13 PID: 130949 Comm: oom01 Not tainted 5.7.0-rc6-next-20200521+ #115
> > > > > [ 3319.284551] NIP: c00000000043027c LR: c000000000430278 CTR: c0000000007bd120
> > > > > [ 3319.284572] REGS: c00000064a42f710 TRAP: 0700 Not tainted (5.7.0-rc6-next-20200521+)
> > > > > [ 3319.284602] MSR: 900000000282b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 28222422 XER: 20040000
> > > > > [ 3319.284638] CFAR: c000000000119098 IRQMASK: 0
> > > > > GPR00: c000000000430278 c00000064a42f9a0 c000000001765500 000000000000001b
> > > > > GPR04: c00000000179c3b0 000000000000000b 0000000066726564 c00000000429ac28
> > > > > GPR08: 0000000000000001 0000000000000000 0000000000000000 c000001301facc80
> > > > > GPR12: 0000000000002000 c000001fffff3d80 0000000000000000 0000000000000000
> > > > > GPR16: 0000000000000000 0000000000000000 c0000014f358dd60 fffffffffff7dfff
> > > > > GPR20: c0000003725a9128 c0000003725a3928 c000000b0a0c0670 c000000b0a0c0678
> > > > > GPR24: c000000b0a0c0660 c00000064a42fa58 c000000b0a0c0650 c0000003725a9080
> > > > > GPR28: 0000000000000001 0000000000000000 c000000001620178 0000000000000001
> > > > > [ 3319.284825] NIP [c00000000043027c] __vm_enough_memory+0x1dc/0x1f0
> > > > > [ 3319.284853] LR [c000000000430278] __vm_enough_memory+0x1d8/0x1f0
> > > > > [ 3319.284872] Call Trace:
> > > > > [ 3319.284889] [c00000064a42f9a0] [c000000000430278] __vm_enough_memory+0x1d8/0x1f0 (unreliable)
> > > > > [ 3319.284930] [c00000064a42fa30] [c000000000114258] dup_mm+0x2a8/0x700
> > > > > [ 3319.284960] [c00000064a42fae0] [c000000000115c7c] copy_process+0xeac/0x1a00
> > > > > [ 3319.284981] [c00000064a42fbf0] [c000000000116b3c] _do_fork+0xac/0xce0
> > > > > [ 3319.285002] [c00000064a42fd00] [c000000000117928] __do_sys_clone+0x98/0xe0
> > > > > [ 3319.285032] [c00000064a42fdc0] [c000000000039e78] system_call_exception+0x108/0x1d0
> > > > > [ 3319.285064] [c00000064a42fe20] [c00000000000c9f0] system_call_common+0xf0/0x278
> > > > > [ 3319.285093] Instruction dump:
> > > > > [ 3319.285109] 60000000 73a90001 4182000c e8be0002 4bfffeb8 3c62ff51 39200001 3d42fff9
> > > > > [ 3319.285142] 38636690 992a6ad6 4bce8dbd 60000000 <0fe00000> e8be0002 4bfffe90 60000000