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Date: Tue, 30 Mar 2021 17:10:36 +0200
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Muchun Song <songmuchun@...edance.com>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>,
Linux Next Mailing List <linux-next@...r.kernel.org>,
Yang Shi <shy828301@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-s390 <linux-s390@...r.kernel.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>,
Shakeel Butt <shakeelb@...gle.com>,
Vladimir Davydov <vdavydov.dev@...il.com>,
Xiongchun Duan <duanxiongchun@...edance.com>
Subject: RE: kernel warning percpu ref in obj_cgroup_release
On 30.03.21 15:49, Muchun Song wrote:
> On Tue, Mar 30, 2021 at 9:27 PM Christian Borntraeger
> <borntraeger@...ibm.com> wrote:
>>
>> So bisect shows this for belows warning:
>
> Thanks for your effort on this. Can you share your config?
attached (but its s390x) for next-20210330
The problem goes away when I add
cgroup_controllers = [ ]
to /etc/libvirt/qemu.conf
The testcase that triggers the problem starts and stops multipe KVM guests with 248 CPUs.
Do we happen to have maybe only a byte of refcount space?
>
>>
>> 636c3ef8229ecb4e7d045e86f36505d24a8f019a is the first bad commit
>> commit 636c3ef8229ecb4e7d045e86f36505d24a8f019a
>> Author: Muchun Song <songmuchun@...edance.com>
>> Date: Mon Mar 29 11:12:06 2021 +1100
>>
>> mm: memcontrol: use obj_cgroup APIs to charge kmem pages
>>
>> Since Roman's series "The new cgroup slab memory controller" applied. All
>> slab objects are charged via the new APIs of obj_cgroup. The new APIs
>> introduce a struct obj_cgroup to charge slab objects. It prevents
>> long-living objects from pinning the original memory cgroup in the memory.
>> But there are still some corner objects (e.g. allocations larger than
>> order-1 page on SLUB) which are not charged via the new APIs. Those
>> objects (include the pages which are allocated from buddy allocator
>> directly) are charged as kmem pages which still hold a reference to the
>> memory cgroup.
>>
>> We want to reuse the obj_cgroup APIs to charge the kmem pages. If we do
>> that, we should store an object cgroup pointer to page->memcg_data for the
>> kmem pages.
>>
>> Finally, page->memcg_data will have 3 different meanings.
>>
>> 1) For the slab pages, page->memcg_data points to an object cgroups
>> vector.
>>
>> 2) For the kmem pages (exclude the slab pages), page->memcg_data
>> points to an object cgroup.
>>
>> 3) For the user pages (e.g. the LRU pages), page->memcg_data points
>> to a memory cgroup.
>>
>> We do not change the behavior of page_memcg() and page_memcg_rcu(). They
>> are also suitable for LRU pages and kmem pages. Why?
>>
>> Because memory allocations pinning memcgs for a long time - it exists at a
>> larger scale and is causing recurring problems in the real world: page
>> cache doesn't get reclaimed for a long time, or is used by the second,
>> third, fourth, ... instance of the same job that was restarted into a new
>> cgroup every time. Unreclaimable dying cgroups pile up, waste memory, and
>> make page reclaim very inefficient.
>>
>> We can convert LRU pages and most other raw memcg pins to the objcg
>> direction to fix this problem, and then the page->memcg will always point
>> to an object cgroup pointer. At that time, LRU pages and kmem pages will
>> be treated the same. The implementation of page_memcg() will remove the
>> kmem page check.
>>
>> This patch aims to charge the kmem pages by using the new APIs of
>> obj_cgroup. Finally, the page->memcg_data of the kmem page points to an
>> object cgroup. We can use the __page_objcg() to get the object cgroup
>> associated with a kmem page. Or we can use page_memcg() to get the memory
>> cgroup associated with a kmem page, but caller must ensure that the
>> returned memcg won't be released (e.g. acquire the rcu_read_lock or
>> css_set_lock).
>>
>> Link: https://lkml.kernel.org/r/20210319163821.20704-6-songmuchun@bytedance.com
>> Signed-off-by: Muchun Song <songmuchun@...edance.com>
>> Acked-by: Johannes Weiner <hannes@...xchg.org>
>> Cc: Michal Hocko <mhocko@...nel.org>
>> Cc: Roman Gushchin <guro@...com>
>> Cc: Shakeel Butt <shakeelb@...gle.com>
>> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
>> Cc: Xiongchun Duan <duanxiongchun@...edance.com>
>> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>> Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
>>
>> include/linux/memcontrol.h | 116 +++++++++++++++++++++++++++++++++++----------
>> mm/memcontrol.c | 110 +++++++++++++++++++++---------------------
>> 2 files changed, 145 insertions(+), 81 deletions(-)
>>
>>
>>
>>
>>
>> On 30.03.21 13:32, Christian Borntraeger wrote:
>> [...]
>>>
>>> This next (328 is fine) triggers several bugs during our KVM CI run:
>>>
>>> [ 1506.494716] ------------[ cut here ]------------
>>> [ 1506.494730] percpu ref (obj_cgroup_release) <= 0 (-1) after switching to atomic
>>> [ 1506.494766] WARNING: CPU: 6 PID: 0 at lib/percpu-refcount.c:196 percpu_ref_switch_to_atomic_rcu+0x1ea/0x1f8
>>> [ 1506.494774] Modules linked in: kvm vhost_vsock vmw_vsock_virtio_transport_common vsock vhost vhost_iotlb xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT xt_tcpudp nft_compat nf_nat_tftp nft_objref nf_conntrack_tftp nft_counter bridge stp llc nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct dm_service_time nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink zfcp scsi_transport_fc rpcrdma sunrpc dm_multipath rdma_ucm scsi_dh_rdac scsi_dh_emc rdma_cm scsi_dh_alua iw_cm ib_cm mlx5_ib ib_uverbs dm_mod ib_core s390_trng vfio_ccw vfio_mdev mdev vfio_iommu_type1 zcrypt_cex4 vfio eadm_sch sch_fq_codel configfs ip_tables x_tables ghash_s390 prng aes_s390 des_s390 libdes sha3_512_s390 sha3_256_s390 mlx5_core sha512_s390 sha256_s390 sha1_s390 sha_common nvme nvme_core pkey zcrypt rng_core autofs4 [last unloaded: vfio_ap]
>>> [ 1506.494832] CPU: 6 PID: 0 Comm: swapper/6 Not tainted 5.12.0-20210330.rc4.git0.9d49ed9ca93b.300.fc33.s390x+next #1
>>> [ 1506.494834] Hardware name: IBM 8561 T01 703 (LPAR)
>>> [ 1506.494836] Krnl PSW : 0704c00180000000 00000002d71dd21e (percpu_ref_switch_to_atomic_rcu+0x1ee/0x1f8)
>>> [ 1506.494840] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
>>> [ 1506.494842] Krnl GPRS: c0000000fffeffff 00000002f7256818 0000000000000043 00000000fffeffff
>>> [ 1506.494844] 00000000ffffffea 0000038000000001 0000000000000000 000003800000017c
>>> [ 1506.494846] 00000002d7924988 0000000227eb97a0 000003ff5413c7e0 7fffffffffffffff
>>> [ 1506.494848] 0000000080360000 00000002f726b570 00000002d71dd21a 00000380000bba28
>>> [ 1506.494856] Krnl Code: 00000002d71dd20e: e3309fe8ff04 lg %r3,-24(%r9)
>>> 00000002d71dd214: c0e5001eb556 brasl %r14,00000002d75b3cc0
>>> #00000002d71dd21a: af000000 mc 0,0
>>> >00000002d71dd21e: a7f4ffcc brc 15,00000002d71dd1b6
>>> 00000002d71dd222: 0707 bcr 0,%r7
>>> 00000002d71dd224: 0707 bcr 0,%r7
>>> 00000002d71dd226: 0707 bcr 0,%r7
>>> 00000002d71dd228: eb6ff0480024 stmg %r6,%r15,72(%r15)
>>> [ 1506.494928] Call Trace:
>>> [ 1506.494933] [<00000002d71dd21e>] percpu_ref_switch_to_atomic_rcu+0x1ee/0x1f8
>>> [ 1506.494940] ([<00000002d71dd21a>] percpu_ref_switch_to_atomic_rcu+0x1ea/0x1f8)
>>> [ 1506.494942] [<00000002d6b8a6c6>] rcu_do_batch+0x146/0x608
>>> [ 1506.494946] [<00000002d6b8ec04>] rcu_core+0x124/0x1d0
>>> [ 1506.494948] [<00000002d75d0222>] __do_softirq+0x13a/0x3c8
>>> [ 1506.494952] [<00000002d6b05306>] irq_exit+0xce/0xf8
>>> [ 1506.494955] [<00000002d75c1eb4>] do_ext_irq+0xdc/0x170
>>> [ 1506.494957] [<00000002d75cdea4>] ext_int_handler+0xc4/0xf4
>>> [ 1506.494959] [<0000000000000000>] 0x0
>>> [ 1506.494963] [<00000002d75cd9c2>] default_idle_call+0x42/0x110
>>> [ 1506.494965] [<00000002d6b411a0>] do_idle+0xd8/0x168
>>> [ 1506.494968] [<00000002d6b413ee>] cpu_startup_entry+0x36/0x40
>>> [ 1506.494971] [<00000002d6ac730a>] smp_start_secondary+0x82/0x88
>>> [ 1506.494974] Last Breaking-Event-Address:
>>> [ 1506.494975] [<00000002d6b71898>] vprintk_emit+0xa8/0x110
>>> [ 1506.494978] Kernel panic - not syncing: panic_on_warn set ...
>>>
>>>
>>>
>>> I will try to bisect this, but if anyone has an idea. CC some candidates.
>>
Download attachment "config-bad.gz" of type "application/gzip" (20017 bytes)
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