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 25CA53F54B4 for ; Mon, 15 Jun 2026 13:22:42 +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=1781529764; cv=none; b=ooMzCsILX3jusuUcVKcjXtd55Mgi4fskoEXJBXH2nYOag9LLeiln5P7/lpQpcLPIFVrW/tErqrv7vSaVFS1AMOsqDgd1KVijubQ6f6H6EV7U1YTwugMBwbKKiGuCLAcMTw5jH9jhBPalIU3aix9apORJHN2QkDfmiHrCob7Nhsk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781529764; c=relaxed/simple; bh=dNioLWu/kYZl5Bcu4Wto65hsgJFP2U+D8HrRPKT/80U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uMWpMBsF3Mj2eoQ+Ug2Nu1yGlDpdXL2nSoUStoo2qscD6Z92uBUbgwijiSW5o0QdCc0NQs3N2NN98HDTAcybl91KxQaVgVAlqe0Mo4itm9qWdcVnjRyP0BA16U23yjdUrgWhsIB8E2k+zmLAueRixVKqyvF9DBFoyHJvDTE0b0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Qal98/d9; 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="Qal98/d9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C4A31F000E9; Mon, 15 Jun 2026 13:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781529762; bh=zNPyLKx7dQGxoDPXTwAxYRlKaYtNc4oSo0QBeDNs1UM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Qal98/d93FUc5mLUGcLIIO88jTJ8hYlOozC7Xoa11TFPHBUDXmI+QK8yYhJxC6xHI 99/zEypMoC4/iJ0RXSEkVI/BbNQO/ucqnmggcjvtuYEXhkGaPY5Jy5igkzhbiOJK16 2ptCHXbaoBjMjScbjx5aCFc83PFUu0CHS3qB2qvznesFNycLlP729IKy4e6rFNQw2D N6TSY2EapYrVTVCJBMmhvzbEJxSlR9nK9kF1BEjhE0vl0aniOfOX1uFVjT4ETC2OJ+ Hbg/k839Asa/7g44vxuZ9LIys0kK365INCPbecbM+QvJNJUSxLzQ7lSoJBElK3Ehiq Khn5+N+8gEiNQ== Message-ID: <17f2f1e7-36ee-4d90-af1c-1fbca6f94025@kernel.org> Date: Mon, 15 Jun 2026 15:22:35 +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 v2 19/22] mm/page_alloc: implement __GFP_UNMAPPED allocations Content-Language: en-US To: Brendan Jackman , Brendan Jackman , Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Wei Xu , Johannes Weiner , Zi Yan , Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, rppt@kernel.org, Sumit Garg , derkling@google.com, reijiw@google.com, Will Deacon , rientjes@google.com, "Kalyazin, Nikita" , patrick.roy@linux.dev, "Itazuri, Takahiro" , Andy Lutomirski , David Kaplan , Thomas Gleixner , Yosry Ahmed References: <20260320-page_alloc-unmapped-v2-0-28bf1bd54f41@google.com> <20260320-page_alloc-unmapped-v2-19-28bf1bd54f41@google.com> <7bfda0d8-2a7a-4337-8b55-d0c158df7839@kernel.org> <4a4470b8-0aeb-4618-8a83-888221965153@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/15/26 15:08, Brendan Jackman wrote: > On Mon Jun 15, 2026 at 1:02 PM UTC, Vlastimil Babka (SUSE) wrote: >>> >>> Full code: >>> https://github.com/bjackman/linux/tree/page_alloc-unmapped-2026-06-11 >>> >>> This makes the regression above (faster OOMs) go away, but it seems like >>> a pretty blunt approach. But then I'm realising I don't really know why it >>> matters? >> >> You mean, why does it matter that we don't OOM prematurely? I'd say that >> matters a lot. >> >>> The main thing is presumably that we are more likely to >>> pointlessly attempt compaction or compact more than we need. But in that >> >> I don't understand why that would be the case? If compaction thinks our goal >> is order-0, there won't be any? >> >> Or you mean that it doesn't matter that your approach above is blunt, and >> are talking about the consequences of that blunt approach? > > Yeah exactly this - it seems to fix the issue, but I dunno if it's > cheating. It _feels_ like cheating but I actually don't know what it > would break - maybe nothing? Ah ok, now I understand. Will have to check more closely if it can break something. Maybe Johannes has some insight as he mentioned working on a similar thing for the defrag mode?