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 86F82376BCD for ; Tue, 24 Feb 2026 10:10:23 +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=1771927823; cv=none; b=sXl8b6TJdIjpcdecG+QF6c844XcuXzy2H+MjzEb2nwhwTGTFHbwVGn2RSPjKjhT+PbYHoB9jHYIlsEhThe1+WvAqrBmolOnSzFDGlbPfuCoG1b/osaDb5OC3I7mTP1RdVY2pELM4iN9x2P0D94i/2CeE89KRGPeVIPgcxcsKlqk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771927823; c=relaxed/simple; bh=HLl0s56QthgFvq5ounX7gaoVLceVUg13LF70lAn+VcA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XMCyfbrV4M++DCyIPKnKo4VS4eMUw4OrlCWWyxUhyttrkVWnU0kzk+yhBrLyHU8O7fBqzYSZseE0ikIZdbVlJ5bQKzOetrDywlECXDI9MWasOfO/Q66ouSDEb4gOmPLt9VLW/9Pnk1DXq8Zwp8qn9FqOssebXM0wxDtILtNYHG8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eUuT//x3; 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="eUuT//x3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36A64C116D0; Tue, 24 Feb 2026 10:10:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771927823; bh=HLl0s56QthgFvq5ounX7gaoVLceVUg13LF70lAn+VcA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=eUuT//x3T18L5U+IYW4yhBmaBd1Hs2QpYgo5OmQczVfNVug3MUE6iNZOvDyCDeD8g gC5xNPPkbEHkCXbqejzoqOW7jwa5C31ubtGYhOFUmDH+BPZxhqMvHjxdNvtkFu7jJx 1vnTa9atEQN4TvD+WtyLtsy0vCv3GWgDnoMWpdxFxbDlwmyN9Qe5U0SeHTgrSm3TCS GrcBvsCxn1SgvRRq/3L/7oK5mA+S3CdhoGpd7VtBgrCZIYF/A3GCF2cEIHcjYhy7hb muv5pUvzmiIBvv5v6RcD8Dt6o5RIwsxzDuAB7IzgEzBpvMSmNwsgM3/0A/RjVz4Fhj ZFWRHqNAfA1KQ== Message-ID: Date: Tue, 24 Feb 2026 11:10:19 +0100 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 mm-new v8 4/4] mm: khugepaged: skip lazy-free folios To: Barry Song <21cnbao@gmail.com> Cc: Vernon Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, dev.jain@arm.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang References: <20260221093918.1456187-1-vernon2gm@gmail.com> <20260221093918.1456187-5-vernon2gm@gmail.com> <658903fb-cf3a-43c3-b8c0-d47b63d10782@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: 8bit On 2/23/26 21:08, Barry Song wrote: > On Mon, Feb 23, 2026 at 9:16 PM David Hildenbrand (Arm) > wrote: >> >> On 2/21/26 14:38, Vernon Yang wrote: >>> >>> In folio_add_new_anon_rmap(), we know that the vma has the VM_DROPPABLE >>> attribute, which is the root reason why Collapsing maintains that property. >>> The above commit log clearly states "all folios in VM_DROPPABLE are lazyfree" >>> ^^^^^^^^^^^^^^^ >>> (the "if" is redundant and should be removed), not "all folios are lazyfree". >> >> >> Exactly. folio_add_new_anon_rmap() makes sure that all folios (except >> the shared zero folios ;) ) in VM_DROPPABLE are lazyfree. >> >> In fact, MADV_FREE should be a NOP on VM_DROPPABLE, as >> folio_mark_lazyfree() doesn't do anything. >> > > Maybe we could do something like the following? > > diff --git a/mm/madvise.c b/mm/madvise.c > index c0370d9b4e23..173b0e5308b5 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -817,6 +817,11 @@ static int madvise_free_single_vma(struct > madvise_behavior *madv_behavior) > range.end = min(vma->vm_end, end_addr); > if (range.end <= vma->vm_start) > return -EINVAL; > + > + /* All folios in the VM_DROPPABLE VMA are already lazyfree */ > + if (vma->vm_flags & VM_DROPPABLE) > + return 0; We could, but it feels like optimizing for a case that likely nobody triggers :) -- Cheers, David