From nobody Fri Oct 10 21:10:18 2025 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 86A0C1EB19B for ; Fri, 13 Jun 2025 03:06:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749783975; cv=none; b=Du2Japu61LH9M/P84/qI2QHDXt4l68I8XDCjkPZ/O3xM9RmAS2v1obTZxALPFEKfMaJ7z5+hmwUIwjyZHIdMFRtHOXlD/3y78b0mpx4WrpqxQqpsDiGKKydZl8L9rvKT2LK1HXA+P3rhCW/qB9MF6a6v935OVptRjiIi36XqoSY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749783975; c=relaxed/simple; bh=d1E72JCG9NdkFhRoVCh+AuOWZQ8c4f7+g6BypUShgPw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Mvp6dYj0bZUc24z5MtP9Xbz8i5pcy2r9t3fEJjoKfKlaQ12K5uuY0Jjk/d4Bh0OaJ8Xch2c+Yb6nVoOZ2Mtlct3gNOqBPLC2FrdynFoxEiKPshPZlvTqpoM/YUN5ifdWQ8cVFr4+g6KQRFgobrretf4lILAsB1F7udp7ltkKT5Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=IRnDQ8ko; arc=none smtp.client-ip=95.215.58.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="IRnDQ8ko" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1749783970; 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: in-reply-to:in-reply-to:references:references; bh=j3zX8MhJa07yqjHNrL6ieLh1aYMQH27ruTr0qMMWaSs=; b=IRnDQ8koDXjvaIA6KMlYvmxXWMvfOTU0iF921IKgbPnUKMpn6dvgPYQnNy6fnowL9kKBD2 7CVTs8oy9THBnY9JcIHml1z9wOx1nsJjysm6RK8nBDBvWa6rxvuQ9dzWS/boC5E3srenYO u0+v/sbFsEfnHtNQHWlQYJC8gnI25cU= 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 v2 1/3] mm/Kconfig: add ARCH_NEEDS_WEAK_PER_CPU Option and enable it for s390/alpha Date: Fri, 13 Jun 2025 11:05:05 +0800 Message-Id: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" 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,MODULE_NEEDS_WEAK_PER_CPU might be a more accurate description. Then,when defining the percpu variable _shared_alloc_tag,wrap it with the CONFIG_ARCH_NEEDS_WEAK_PER_CPU condition. Therefore,we should add the ARCH_NEEDS_WEAK_PER_CPU option to the mm Kconfig file and enable it for the s390 and alpha architectures. Suggested-by: Suren Baghdasaryan Signed-off-by: Hao Ge --- arch/alpha/Kconfig | 1 + arch/s390/Kconfig | 1 + mm/Kconfig | 4 ++++ 3 files changed, 6 insertions(+) diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index 109a4cddcd13..ce9bc842e384 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -7,6 +7,7 @@ config ALPHA select ARCH_HAS_DMA_OPS if PCI select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO + select ARCH_NEEDS_WEAK_PER_CPU select ARCH_NO_PREEMPT select ARCH_NO_SG_CHAIN select ARCH_USE_CMPXCHG_LOCKREF diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 0c16dc443e2f..716031d22346 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -132,6 +132,7 @@ config S390 select ARCH_INLINE_WRITE_UNLOCK_IRQ select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE + select ARCH_NEEDS_WEAK_PER_CPU select ARCH_STACKWALK select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEBUG_PAGEALLOC diff --git a/mm/Kconfig b/mm/Kconfig index e113f713b493..2f55cc95cfcb 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -929,6 +929,10 @@ config ARCH_SUPPORTS_PUD_PFNMAP def_bool y depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD =20 +# s390 and alpha should be enabled,see comments for DECLARE_PER_CPU_SECTION +config ARCH_NEEDS_WEAK_PER_CPU + bool + # # UP and nommu archs use km based percpu allocator # --=20 2.25.1