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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1749714942; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=6LY4vo/bZ3YMDxVE6i6Ie0OrWW95nPMauCx+hjveabo=; b=pAt24u3e6DtqHI3n6q714oL8sqKPM+Ragc6XP+y6q755JG00eCl7OA+DlnvcPn+25YcBxJ juQr09jumKVG3bXGKcS4eMhi5pCXVXD1jxh+2oWhewoqv3uHp1ewyRGSiHelHz4vt7/eTN blBCVG4IA6VWg16y48+NCwpOQ4HC2jE= From: Hao Ge To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Mike Rapoport , Richard Henderson , Matt Turner , Dennis Zhou , Tejun Heo , Christoph Lameter , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Kent Overstreet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-s390@vger.kernel.org, Hao Ge , Hao Ge Subject: [PATCH 0/5] mm: Restrict the static definition of the per-CPU variable _shared_alloc_tag to s390 and alpha architectures only Date: Thu, 12 Jun 2025 15:54:23 +0800 Message-Id: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C904E8000E X-Stat-Signature: q7odgfrr7rg1tj3g4hsfpkcyw4y7myqz X-Rspam-User: X-HE-Tag: 1749714944-499366 X-HE-Meta: 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 IUUgfDL9 /O11FpY7GZxV4ZL+h3B7ok16Q00TZTEFafdu3/AAPF1UlbQ02ocAnlJe8EBdeRgTEbW/RS8BZkV/s3V1e25K+qBJzhPKKX/CcSiyWOB0i2s8URCjmV853SjfsQVur3EMdKoxoGsKRKv/4Z/3hacsYev6+RIaZl+6nRIkmXae8Cp+l0rBJJ1c7eyjEVsWGEffahBSQ12i8JOPEpV9vADb1Cap9Muui8fE1CG7khrsmYyFBtIiFGU3Akvg/YuY2KoE8Z+17yUP6m3+XK+k9mgsAbVEnuWhI89gjkwvA X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Hao Ge Recently discovered this entry while checking kallsyms on ARM64: ffff800083e509c0 D _shared_alloc_tag If ARCH_NEEDS_WEAK_PER_CPU is not defined((it is only defined for s390 and alpha architectures),there's no need to statically define the percpu variable _shared_alloc_tag. As the number of CPUs increases,the wasted memory will grow correspondingly. Therefore,we need to implement isolation for this purpose. However,currently ARCH_NEEDS_WEAK_PER_CPU is a #define and is enclosed within the #if defined(MODULE) conditional block. When building the core kernel code for s390 or alpha architectures, ARCH_NEEDS_WEAK_PER_CPU remains undefined (as it is gated by #if defined(MODULE)). However,when building modules for these architectures,the macro is explicitly defined. Therefore,we need to make ARCH_NEEDS_WEAK_PER_CPU a Kconfig option. And replace all instances of ARCH_NEEDS_WEAK_PER_CPU in the kernel code with MODULE_NEEDS_WEAK_PER_CPU,gated by#ifdef CONFIG_ARCH_NEEDS_WEAK_PER_CPU. Then,when defining the percpu variable _shared_alloc_tag,wrap it with the CONFIG_ARCH_NEEDS_WEAK_PER_CPU condition. The following version could be regarded as Version 1: https://lore.kernel.org/all/20250529073537.563107-1-hao.ge@linux.dev/ But unfortunately,it caused build errors on s390. Based on Suren's guidance and suggestions, I've refined it into this patch series. Many thanks to Suren for his patient instruction. Verify: 1. On Arm64: nm vmlinux | grep "_shared_alloc_tag",no output is returned. 2. On S390: Compile tested. nm vmlinux | grep "_shared_alloc_tag" 00000000015605b4 r __crc__shared_alloc_tag 0000000001585fef r __kstrtab__shared_alloc_tag 0000000001586897 r __kstrtabns__shared_alloc_tag 00000000014f6548 r __ksymtab__shared_alloc_tag 0000000001a8fa28 D _shared_alloc_tag nm net/ceph/libceph.ko | grep "_shared" U _shared_alloc_tag 3. On alpha Compile tested. nm vmlinux | grep "_shared_alloc_tag" fffffc0000b080fa r __kstrtab__shared_alloc_tag fffffc0000b07ee7 r __kstrtabns__shared_alloc_tag fffffc0000adee98 r __ksymtab__shared_alloc_tag fffffc0000b83d38 D _shared_alloc_tag nm crypto/cryptomgr.ko | grep "_share" U _shared_alloc_tag Hao Ge (5): mm/Kconfig: add ARCH_NEEDS_WEAK_PER_CPU option alpha: Modify the definition logic of WEAK_PER_CPU s390: Modify the definition logic of WEAK_PER_CPU mm: use MODULE_NEEDS_WEAK_PER_CPU instead of ARCH_NEEDS_WEAK_PER_CPU mm/alloc_tag: add the CONFIG_ARCH_NEEDS_WEAK_PER_CPU macro when statically defining the percpu variable _shared_alloc_tag arch/alpha/Kconfig | 1 + arch/alpha/include/asm/percpu.h | 4 ++-- arch/s390/Kconfig | 1 + arch/s390/include/asm/percpu.h | 4 ++-- include/linux/alloc_tag.h | 6 +++--- include/linux/percpu-defs.h | 4 ++-- lib/alloc_tag.c | 2 ++ mm/Kconfig | 4 ++++ 8 files changed, 17 insertions(+), 9 deletions(-) -- 2.25.1