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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1762919922; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QN5OS2KvdscboVyOnBEkHw4P/EaV6sHWrdSW/m7H7Cg=; b=1TWyz9ci+OVwShW7rOBgMhoU6/tDKa23S46mPhW3682qmUlxHKmbUXFuIRjotvStd1KlK9 2v+vghxLgWKQaX1MhRm9V5VMd6x9/Q50wPFZfKUejI3lq7oxOZEQBKUV9bjLOxzGDCrdE1 tCVnJNrpSt1M5/rvpAN/SEcKOWo3gfY= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 02C961515; Tue, 11 Nov 2025 19:58:33 -0800 (PST) Received: from [10.164.136.35] (unknown [10.164.136.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1DD7B3F5A1; Tue, 11 Nov 2025 19:58:36 -0800 (PST) Message-ID: <811bea18-30d0-446f-8840-d99698a6a9ba@arm.com> Date: Wed, 12 Nov 2025 09:28:34 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/khugepaged: continue to collapse on SCAN_PMD_NONE To: Wei Yang , Lance Yang Cc: linux-mm@kvack.org, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, npache@redhat.com, baohua@kernel.org, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com References: <20251112020031.25350-1-richard.weiyang@gmail.com> <06096f8b-4da0-4b5c-af3c-fd8871437c16@linux.dev> <20251112034008.ojwghkko74psu65v@master> Content-Language: en-US From: Dev Jain In-Reply-To: <20251112034008.ojwghkko74psu65v@master> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 083CB180004 X-Rspamd-Server: rspam07 X-Stat-Signature: qp7q3w5byxdfepnsxh5uwfi5urdwin4b X-Rspam-User: X-HE-Tag: 1762919921-288217 X-HE-Meta: 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 moq+9oU2 YdLiCECmJIvpL5gJFgDyM+p6D162WwdIELKCdy1g9LoI+U0f9vSzsKxk+fvRIqyVZVk754hp3DcReYjEGDa3CmUaAdb4LN6bnnt3youpokxpyrZe7/DkFNVMhgmvjyVh/xXtVrRrd4XuRK0jJtj+4Nm4oLkg9Q7DHIHTO+DTCPKcgvfObgzv621c1UBqNaKEYVIGc8uxLGvKLFVorNV8Cx2JKBFkFZF+di1YQL66lNKhepgtvbcf3v3iaeGdaEN8kqxRvVLdD/VyYLMftbEyndwtUtWSk6h+zRhPOKw9cdpZv0HKGkACVojBObg== 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: On 12/11/25 9:10 am, Wei Yang wrote: > On Wed, Nov 12, 2025 at 10:37:06AM +0800, Lance Yang wrote: >> >> On 2025/11/12 10:00, Wei Yang wrote: >>> SCAN_PMD_NONE means current pmd is empty, but we can still continue >>> collapse next pmd range. >> Right, bailing out of the whole MADV_COLLAPSE request just because >> we encounter one empty PMD is too strict ... >> >> It makes sense to treat SCAN_PMD_NONE like the other whitelisted cases >> (e.g., SCAN_PMD_NULL). >>> Signed-off-by: Wei Yang >>> --- >> LGTM. >> >> Reviewed-by: Lance Yang >> > Thanks for the review. > > I'm currently evaluating the use of SCAN_NULL versus SCAN_NONE. It seems their > usage in the current code is intermixed, and I'm questioning if there's a > strong, practical reason to maintain a distinction between these two states. > Should they be unified? There was some discussion about that in this thread: https://lore.kernel.org/all/v5ivpub6z2n2uyemlnxgbilzs52ep4lrary7lm7o6axxoneb75@yfacfl5rkzeh/ There are some cleanups mentioned in the thread which you can try if you want :)