From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4FBF1266581; Mon, 27 Apr 2026 19:37:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777318632; cv=none; b=eIeDnpoCFutVtF2JmueeYUMUkbEx/zAIJTghluOZ6/2JzJ5WKwvpkumMAHviT/Fo/1zn4h3fYYt8xdnAn7HHv8xbmrsvZZ7xDFZsbwTSs4Rwdy2oDzIJt1GhXY/YGvH/vb1qakxp2zQ1TCYNsOx0goQf+0083oI/bfP4DcECUyI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777318632; c=relaxed/simple; bh=sYmKObJMhnp7jy264AilvXj9lD+eqjDwhHG7MFsMTtA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W8WDpjbxkfaNSLBACqTJw9f6rwcloP/oWdHUJjrepUQkPwHJFlv8NsPGQcx6RS/sp4v8dvGgpr9faM15KvQHgSxvLB+7IiVgY4BlwUmz1v7rzd0eIvzBqvQCcctgSGWwrkh+I6gSNmLHdDDrs4yKxFBVfjRihFdAVuiRcRG4hSo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EfhmJXK2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EfhmJXK2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73861C19425; Mon, 27 Apr 2026 19:37:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777318632; bh=sYmKObJMhnp7jy264AilvXj9lD+eqjDwhHG7MFsMTtA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=EfhmJXK2MOebbFDynHs0e6ErEa+rR2fV5oPwMls7eMi5DhkgqFFrMxyutV36q8HmK jSOorctS20K28WCUspXTRYb6tn6OjdGbIrPSo/Oq21tzGBI1fVdXH29EPZAw5RHoke DDQQzzqBy+mYBUVQFpdpoTNB/XeWlNDii5FuiXObRKRN1CxRqGeg22rkLk+vtIdxoK 34seLrxMRA/Xg++UkPSqlQ6X/KUl4EX6WlLr+aGuczFFTAYeOp/UN5KEL8U7y+j+Wc c9PtR7/0VgsfXri/FktT7d6SBqQxteh482P1+7pQVyl/LS/tn12GXvHgprGuk8/hbM 7VZxkVldOZhPw== Message-ID: <36d82055-67f3-4c29-a605-a9848a28f7cb@kernel.org> Date: Mon, 27 Apr 2026 21:37:02 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 4/7] mm: add page consistency checker implementation To: Sasha Levin Cc: Pasha Tatashin , akpm@linux-foundation.org, corbet@lwn.net, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, skhan@linuxfoundation.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Sasha Levin , Sanif Veeras , "Claude:claude-opus-4-7" References: <4b961a07-b72d-4c8a-ab49-23f61ed12b53@kernel.org> <12985b32-88b3-47ab-8292-2e0ec6f5fbae@kernel.org> <3146ebcf-5649-44a7-aa21-163bf404c42b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit >> >> Thanks, but I fundamentally don't understand how RAS capabilities interact here? >> We have mm/memory-failure.c for a reason :) > > We do, but self driving safety requires way more than the current hardware can > provide. > > I'll point you to https://dl.acm.org/doi/10.1145/2775054.2694348 , which > researched these issues in a datacenter environment (so no sun exposure, > temperature controlled, designed to avoid electromagnetic interference). > > "We call a fault that generates an error larger than 2 bits in an ECC word an > undetectable-by-SECDED fault. A fault is undetectable-by-SECDED if it affects > more than two bits in any ECC word, and the data written to that location does > not match the value produced by the fault." > > [...] > > "A Cielo node has 288 DRAM devices, so this translates to 6048, 518, and 57.6 > FIT per node for vendors A, B, and C, respectively. This translates to one > undetected error every 0.8 days, every 9.5 days, and every 85 days on a machine > the size of Cielo." > > [...] > > "Our main conclusion from this data is that SEC-DED ECC is poorly suited to > modern DRAM subsystems. The rate of undetected errors is too high to justify > its use in very large scale systems comprised of thousands of nodes where > fidelity of results is critical." Yes, I read before that ECC is insufficient to detect certain bitflips. But I don't understand how this patch set here is going to move the needle in any reasonable way? You have your magical self-driving car algorithm. Bitflips can corrupt your algorithm, your data, the kernel image, your user page tables, your kernel page tables. Even a pointer to a bitmap :) ... and we worry about the state of allocated vs. free pages. Please enlighten me! > > The passengers you've mentioned before would be excited if they knew how high > the bar is around their safety :) Heh :) -- Cheers, David