From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7D7DF376A1F for ; Mon, 27 Jul 2026 14:21:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785162067; cv=none; b=MOSt4z8ixNYiEQGQnvVnuXXNX/JYWkBUPD6uDMaL/I8RthJbbAjkSWeZZa/LTQgjuCS8gVJCjJbc8/VsaliQWld5MsbM0qwLTPJIYTcrnyzS97TXoxI3igaCx54hNGXhJvZsygjnPDxpRM8FPzAKUxtikV8yjWDQxRP2ytOGU0U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785162067; c=relaxed/simple; bh=Q7mUSk1vRpaOJ8vQO/vZgFxE/pAh4kTsaefp86SMVyI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZtLMBsfFxVvj3UVJTpzUJEIMsg0mQKNVwAIw5yOIHSBkTdkyu9TVVYuscjKG+/CwYRGm9FxC5fu2GOwAyDfE6O2upGOn5fQn7AC+9QqAGe3tTnmpXr4qiX3z/oq1x9cYcpITYr2Xx3YcEteyjYi1EeVv74C2EiSZ+b+Jgp4pKRM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q261pOzq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q261pOzq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 899EC1F000E9; Mon, 27 Jul 2026 14:20:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785162066; bh=L8YMIiupRbSXknhF/gUGXduHBqtF9qvx9Rn5OJ7l7qg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Q261pOzqDy+B8Ff3jFanfTrvyKm/idwoi8pMCcZLKo778FlycP7l4gb8vqXlFIFc7 88ivA90+P1kxfFJb+iCmup+XTuzTIjHNCLlTSmSr3FJ8XnWzTwL3H2kNTkTwqpz8hr xXkK/ltoTpaxLwaycidA2l5yvWhiSW/LPgVkX5ZfOTPx6PckJujePtwGdfrGnVnv7E 4kKo00QcVJkXBuH7+Y1QWE9e0dRmqghOPAHff8HJ1Du0yxihOKjxbh9U0IGPcQdLDN ovKcH55oJJEODbR3xCnO20gApkJEPYT/aK/26PeaJ2xOyAjgoGB4swKj5uvJaACMg6 wEBQtVKrb78gw== Message-ID: <168ad406-f6b5-4623-adac-9f894e410e48@kernel.org> Date: Mon, 27 Jul 2026 16:20:54 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/5] Only free healthy pages in high-order has_hwpoisoned folio To: "Vlastimil Babka (SUSE)" , William Roche , Jiaqi Yan , linmiaohe@huawei.com, ljs@kernel.org, ziy@nvidia.com Cc: osalvador@kernel.org, harry.yoo@oracle.com, willy@infradead.org, osalvador@suse.de, jackmanb@google.com, hannes@cmpxchg.org, nao.horiguchi@gmail.com, tony.luck@intel.com, wangkefeng.wang@huawei.com, jane.chu@oracle.com, akpm@linux-foundation.org, muchun.song@linux.dev, liam@infradead.org, rientjes@google.com, duenwen@google.com, jthoughton@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, shuah@kernel.org, surenb@google.com, mhocko@suse.com, boudewijn@delta-utec.com References: <20260705180714.3708947-1-jiaqiyan@google.com> <85cb7ea8-8116-4092-8310-69b61eb8602c@kernel.org> <1dea7b3c-7740-474d-b9d4-cd2baf47f181@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 On 7/22/26 10:27, Vlastimil Babka (SUSE) wrote: > On 7/17/26 15:06, William Roche wrote: >> On 7/17/26 12:18, David Hildenbrand (Arm) wrote: >>> >>> I still don't like the complexity of this, in particular, as we have different >>> mechanisms in the page allocator already to try handling this, >>> >>> We also do have cases where we set the hwpoison bit, while a page is just about >>> to get allocated from the buddy. So before we take it off the buddy, we might >>> just hand out the page. >>> >>> check_new_pages() seems to check for PageHWPoison() and make us not hand out >>> such pages. It's guarded by "check_pages" but it seems to do exactly what we are >>> looking for, now? >> >> >> Just adding a comment about this aspect: >> The check_new_pages() mechanism used by the __rmqueue functions should >> filter these pages out, but this has been disabled by default in 2023 >> with: >> [PATCH] mm, page_alloc: reduce page alloc/free sanity checks >> https://lore.kernel.org/all/20230216095131.17336-1-vbabka@suse.cz >> >> So it would need to be enabled back, taking some of the performance hit. >> (and I personally think that it has to be done) > > Would it truly fix the issue, or rather there would still be a race window > left where we check that there's no hwpoison flag in the re-enabled check, > and only then someone sets it? Why are we checking PageHWPoison at all then in check_new_page()? I think we created a mess. The PageHWPoison check is not just a "nice to have" sanity check for kernel bugs. So it should never have been optimized out that way before reworking the bigger picture. > > Also, can the hardware actually detect a problem with a page that nobody > accesses? I guess if yes, it's only in some corner cases. Yes, quite frequently I think. > > So I'm wary about penalizing the allocator paths again. I get the feeling that we don't have a proper plan on how to handle HWPoisoned pages. We should take a step back and discuss how we actually want to handle them instead of optimizing here and there and creating more of a mess. -- Cheers, David