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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-02-26 10:42, Mathieu Desnoyers wrote: > On 2026-02-26 10:00, Mathieu Desnoyers wrote: >> On 2026-02-26 07:04, Heiko Carstens wrote: >>> 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 >>> AuthorDate: Tue Feb 17 11:10:06 2026 -0500 >>> Commit:     Andrew Morton >>> 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 >> >> It looks like either an issue with ordering of the bootup sequence, or >> an issue with the size of struct mm_struct init_mm. I'll have a look. > > I've successfully booted a linux-next 7.0.0-rc1-next-20260226 within a > x86-64 vm, with a swap partition. > > I wonder if s390x somehow alters the value of nr_cpus_ids late in > bootup, after percpu_counter_tree_subsystem_init() ? > > Can you share your .config and kernel command line arguments ? I've successfully booted a defconfig s390x next-20260226 kernel in qemu with 1 and 4 CPUs, and within a nested s390x VM on 2 cpus. I guess I'll really need more info about your specific .config and command line args to help further. Thanks, Mathieu > > Thanks, > > Mathieu > -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com