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McKenney" , Steven Rostedt , Masami Hiramatsu , Dennis Zhou , Tejun Heo , Christoph Lameter , Martin Liu , David Rientjes , christian.koenig@amd.com, Shakeel Butt , SeongJae Park , Michal Hocko , Johannes Weiner , Sweet Tea Dorminy , Lorenzo Stoakes , "Liam R . 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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 10:00, 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 ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com