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 <[email protected]>
AuthorDate: Tue Feb 17 11:10:06 2026 -0500
Commit: Andrew Morton <[email protected]>
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
