From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.210.180 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793254082; b=nu92i0UUid1uxQCAOvAsvNPXmoRNlnzIJkGzL17HffNWmoBCFTwOZe8DtQnHZx4u3qjx 7gWMOTCpcmK5ysnIYSQp4zYcX6jmTVpYfPgG4j0WBfZtxyjUtGAeikJmOnEbsjFqIGAEi 9EXccJWBoHf8L11EeyekB+FzEw7Xg3bvmKmQSgp6xlMga54Sd5X2QQq0sJXQfrg+lqLvH sha7a5KlQVtpSm1o8j1UUz1RVr5qC2m0jK0AjdoJdUAUMx+p9m13ot+q5hBi3WWa4USNn KOtGEqBEIGVp6g8OVAM9Edds2qNNqoyxA0DQeCcG2VXDj8+wctUfW6hJuCYLInW/y9g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793254082; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To:User-Agent; bh=KIyRNW6At3oCihbJNccAaO3bWJ8LNw9lR1egadV9gDM=; b=UeliQnXQ+DCuTFEWx9OXQQPlWEB7piVSOcco5Fe93uzzrMb048h4vSLdoQr7nFZdCKXC vGz+78VBLcOMGb9q5tID80R4nRb+zPDPiEqGdimmOOie/IRJhFOhKgmltdYAEH4Od0vPz aQZZPo8pw1mycUT85u/PWJmjkZ542dYTYUgYkcB7GWiZyLLwhIM7gglIr2CZ6wXzHBSlb Q1oUQJOkToWFCiiLfCaOdenUiMuouRyOZp8SBARLO/CUd9rMGQFVNsQwSCQubcSQmAkfr 9xy1XbawJpouwyfHY+qtpTdLoFXWKa2Wb6MGVkYEGpTTBroHxtXFVbViOewfurDfkcg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=chrisdown.name; spf=pass smtp.mailfrom=chrisdown.name; dkim=pass header.d=chrisdown.name header.i=@chrisdown.name header.a=rsa-sha256 header.s=google header.b="I/xnC8+n"; arc=none smtp.remote-ip=209.85.210.180 Received: from mail-pf1-f180.google.com (mail-pf1-f180.google.com [209.85.210.180]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 11294606A31C for ; Thu, 29 Oct 2026 06:08:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 11294606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chrisdown.name Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=chrisdown.name header.i=@chrisdown.name header.a=rsa-sha256 header.s=google header.b=I/xnC8+n Received: by mail-pf1-f180.google.com with SMTP id d2e1a72fcca58-8a07078200fso912014b3a.2 for ; Wed, 28 Oct 2026 23:08:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; t=1793254081; x=1793858881; darn=vger.kernel.org; h=user-agent:in-reply-to:content-disposition:content-type :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to:content-type; bh=KIyRNW6At3oCihbJNccAaO3bWJ8LNw9lR1egadV9gDM=; b=I/xnC8+nPsymSUHPSCVMndHbMjYrHGaw/y9W97v/V/2TNEsAbBBtCC0eACd7C6iOiB ASuuEHniK+dy6GiylaKYvhwWBE9+sneWyYMdevPhbS4Ji19fDeXXk1rT00IZNjslxLMk Ei6Ot5AsDmBrSOlXrS725Y2BufoI2xfgpZUi4= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793254081; x=1793858881; h=user-agent:in-reply-to:content-disposition:content-type :mime-version:references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=KIyRNW6At3oCihbJNccAaO3bWJ8LNw9lR1egadV9gDM=; b=UoKiUM2ApRkoj2EfLZgt3T7OibEXRHevAeNdvYWA2Y1oM3G8Lb8F34YtgyQqAj9l1d Yg33liFh925zr/M/HtXoMOrjYYZs58TKeIdfyAhdgfyYNxEnZJ/O8QcDlVnbd0kWfAgl fkv3YqeVwwiW1fXMdOCS3bRdbN8RI9i+F65T8i+HI6mWD8fmGJPH1nikBuYSkX/15l3P HY3G2IYy/co4KCyw9EYAarQ+msVApxZFEaUrewyCrDOsF3rhyTVMzpppHiRXFvICY/kW wW8GlBuhhlabanHG6DuTctdigHPcAaQVqL0s3yWD6f72vIE01t4xDdLX+P8WSUWtPpE9 rZjA== X-Forwarded-Encrypted: i=1; AKwUvBwF5kBO8aDrPCYCGBzot0wZAJR9MnWJTSmVFWcxcjWYgx9igVrpP5bLRe5TR4eyFevuQZCcuH4ivvsljGU=@vger.kernel.org X-Gm-Message-State: AFq9FYLNxvGTvCXC+ACApqeeP/i3tVHpwWu1hlzRWaA37IzyY0Qyf08f fHEa5T3lD1s3b2n74Ttd4u16bt9B7uQ9pCwpadxSrzLLp6qdgjAQxtgdb20+ntzuClKz3KfMI9k dTdRpxqtMV8UB X-Gm-Gg: AYBFou3oFWErFKmuRScb7BhjF1DbTYiilg2kcn6LSObTOVB1LYRlIXmyzIJjMAzGaYu PAafaQQmslNHLzpWmjM7fltgmSk2/MMDzGBdSiYKEzcul0dBWxGLs0u4sRbkgeXZ3ZrcRepGMWO yvscWwr1PMRDMuGvGekUxKHU77Im9GEpDmVKZR8Xbl2F9Z/RAbXydpn5rX/ay8HLW/1hv2fDn6X JRdQ+y6nNU4q9s6qXJGRZb/qmC8xQGu38aVC2+E1OZ9JUyxbJLigppaj954aP+Q8RjnhlV4UNS6 Yq9YwmxPKfI6kJ+dpGOJncHJwDEuroEcUFtxpr/PdNeuGbxzNFsleRUK5oDVi48p69uNryXoxnH ILxd3hHT4xgEjCrsSfHmjtW6Zf5vWfRfhot9QJpTtk5f4Dm8hfU397Ox/0vHB+D62t+j6+JMWFT 6SzmxKKGoFl+i1tcgIRTzIzahy9s1aek1XdfOaVIWfsZy6LYAtYJViVKJ0IB6+iOrzRFcvfQuLf cRbqYrA2rKBqcDPrbd66JBYtB6Hmj9qQ+08iUfZPjLRxlCSm1gbFF5HaQ4tgwU5hRI0lMf2hJ6t PodHsl8ZyKwMmTAkMH6wEvCcl+uILFT0bNd3S8D0KCYPJ0n1vwm/g1inYY9zunoVWzCajGNjolm RDfBUdVa5gQJWTmt4H0ZhfR6+kQN0WsVERa/PSd2rAxcWLrZzDLNrookD3XZpWcs1zkHI+COa X-Received: by 2002:a05:6a00:a0f:b0:886:5f48:3fca with SMTP id d2e1a72fcca58-8a6e7dc9293mr3736944b3a.37.1793254081351; Wed, 28 Oct 2026 23:08:01 -0700 (PDT) Received: from localhost ([116.86.153.182]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8a6a3d5bd6asm1861640b3a.4.2026.10.28.23.08.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 23:08:00 -0700 (PDT) Date: Thu, 29 Oct 2026 14:07:55 +0800 From: Chris Down To: Vlastimil Babka , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Kees Cook , Marco Elver , GONG Ruiqi , Jonathan Corbet , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH v2 2/6] mm/slab: Enable SLAB_FREELIST_RANDOM by default Message-ID: <6bdc161bd869ead04b3b9a651ef6a83882ecbea3.1793253633.git.chris@chrisdown.name> References: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.3.3 (9073d26d) (2026-06-12) SLAB_FREELIST_RANDOM randomises the order in which the objects in a new slab are handed out. Like SLAB_FREELIST_HARDENED, most distros already enable it, and its cost is only paid when a new slab is set up. With it on, the same system level benchmarks didn't change measurably. Allocating from new slabs does get slower, by up to about 30% per object in a microbenchmark which does little else. So let's enable it by default too. SHUFFLE_PAGE_ALLOCATOR defaults to SLAB_FREELIST_RANDOM && ACPI_NUMA, so it's now built in by default on those systems, but page shuffling itself stays off unless it's enabled with page_alloc.shuffle. Suggested-by: Vlastimil Babka Signed-off-by: Chris Down --- mm/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/Kconfig b/mm/Kconfig index 17d017e8fbef..92ff97ff24fb 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -200,6 +200,7 @@ config SLAB_MERGE_DEFAULT config SLAB_FREELIST_RANDOM bool "Randomize slab freelist" depends on !SLUB_TINY + default y help Randomizes the freelist order used on creating new pages. This security feature reduces the predictability of the kernel slab -- 2.54.0