From: Heiko Carstens <hca@linux.ibm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux.com>,
Martin Liu <liumartin@google.com>,
David Rientjes <rientjes@google.com>,
christian.koenig@amd.com, Shakeel Butt <shakeel.butt@linux.dev>,
SeongJae Park <sj@kernel.org>, Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Sweet Tea Dorminy <sweettea-kernel@dorminy.me>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R . Howlett" <liam.howlett@oracle.com>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Christian Brauner <brauner@kernel.org>,
Wei Yang <richard.weiyang@gmail.com>,
David Hildenbrand <david@redhat.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Al Viro <viro@zeniv.linux.org.uk>,
linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org,
Yu Zhao <yuzhao@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Mateusz Guzik <mjguzik@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Aboorva Devarajan <aboorvad@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
linux-s390@vger.kernel.org
Subject: Re: [PATCH v17 0/3] Improve proc RSS accuracy
Date: Thu, 26 Feb 2026 13:04:22 +0100 [thread overview]
Message-ID: <20260226120422.8101Cc2-hca@linux.ibm.com> (raw)
In-Reply-To: <20260217161006.1105611-1-mathieu.desnoyers@efficios.com>
On Tue, Feb 17, 2026 at 11:10:03AM -0500, Mathieu Desnoyers wrote:
> This series introduces the hierarchical tree counter (hpcc) to increase
> accuracy of approximated RSS counters exposed through proc interfaces.
>
> With a test program hopping across CPUs doing frequent mmap/munmap
> operations, the upstream implementation approximation reaches a 1GB
> delta from the precise value after a few minutes, compared to a 80MB
> delta with the hierarchical counter. The hierarchical counter provides a
> guaranteed maximum approximation inaccuracy of 192MB on that hardware
> topology.
>
> This series is based on
> commit 0f2acd3148e0 Merge tag 'm68knommu-for-v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu
>
> The main changes since v16:
> - Dropped OOM killer 2-pass task selection algorithm.
> - Introduce Kunit tests.
> - Only perform atomic increments of intermediate tree nodes when
> bits which are significant for carry propagation are being changed.
This seems to cause crashes with linux-next on s390, at least I could bisect
it to the last patch of this series. Reverting the last one, makes the crashes
go away:
0acac6604c1cfd7a1762901f0a4abe87cf3a8619 is the first bad commit
commit 0acac6604c1cfd7a1762901f0a4abe87cf3a8619 (HEAD)
Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
AuthorDate: Tue Feb 17 11:10:06 2026 -0500
Commit: Andrew Morton <akpm@linux-foundation.org>
CommitDate: Tue Feb 24 11:15:15 2026 -0800
mm: improve RSS counter approximation accuracy for proc interfaces
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 766d615f72615000 TEID: 766d615f72615803 ESOP-2 FSI
Fault in home space mode while using kernel ASCE.
AS:000000025dc04007 R3:0000000000000024
Oops: 0038 ilc:2 [#1]SMP
Modules linked in:
CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-20260224.rc1.git266.3ef088b0c577.300.fc43.s390x+next #1 PREEMPTLAZY
Hardware name: IBM 3931 A01 703 (z/VM 7.4.0)
Krnl PSW : 0704c00180000000 00000216ef164cde (kernfs_name_hash+0x1e/0xb0)
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
Krnl GPRS: 0000000000000000 0000000000000000 766d615f72615f65 0000000000000000
766d615f72615f65 0000000000000000 0000000000000000 0000000000000000
766d615f72615f65 0000000081212440 0000000000000000 0000000000000000
0000000080a00000 00000216efcb5390 00000216ef16530c 00000196eeb07ae0
Krnl Code: 00000216ef164cd2: a7190000 lghi %r1,0
00000216ef164cd6: b9040042 lgr %r4,%r2
*00000216ef164cda: a7090000 lghi %r0,0
>00000216ef164cde: b25e0014 srst %r1,%r4
00000216ef164ce2: a714fffe brc 1,00000216ef164cde
00000216ef164ce6: b9e92051 sgrk %r5,%r1,%r2
00000216ef164cea: ec1200208076 crj %r1,%r2,8,00000216ef164d2a
00000216ef164cf0: b9160005 llgfr %r0,%r5
Call Trace:
[<00000216ef164cde>] kernfs_name_hash+0x1e/0xb0
[<00000216ef167d32>] kernfs_remove_by_name_ns+0x72/0x120
[<00000216ef16bbfa>] remove_files+0x4a/0x90
[<00000216ef16bf96>] create_files+0x276/0x2b0
[<00000216ef16c15a>] internal_create_group+0x18a/0x320
[<00000216f09b61c6>] swap_init+0x5e/0xa0
[<00000216eec7fb00>] do_one_initcall+0x40/0x270
[<00000216f0990a40>] kernel_init_freeable+0x2b0/0x330
[<00000216efb5160e>] kernel_init+0x2e/0x180
[<00000216eec81ffc>] __ret_from_fork+0x3c/0x240
[<00000216efb5e052>] ret_from_fork+0xa/0x30
Last Breaking-Event-Address:
[<00000216ef165306>] kernfs_find_ns+0x76/0x140
Kernel panic - not syncing: Fatal exception: panic_on_oops
next prev parent reply other threads:[~2026-02-26 12:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-17 16:10 Mathieu Desnoyers
2026-02-17 16:10 ` [PATCH v17 1/3] lib: Introduce hierarchical per-cpu counters Mathieu Desnoyers
2026-02-17 16:10 ` [PATCH v17 2/3] lib: Test " Mathieu Desnoyers
2026-02-17 16:10 ` [PATCH v17 3/3] mm: Improve RSS counter approximation accuracy for proc interfaces Mathieu Desnoyers
2026-02-26 12:04 ` Heiko Carstens [this message]
2026-02-26 15:00 ` [PATCH v17 0/3] Improve proc RSS accuracy Mathieu Desnoyers
2026-02-26 15:42 ` Mathieu Desnoyers
2026-02-26 16:51 ` Andrew Morton
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