From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A14D6C282DE for ; Wed, 5 Mar 2025 19:39:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8CA4D28000F; Wed, 5 Mar 2025 14:39:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 87EC7280008; Wed, 5 Mar 2025 14:39:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 71DD228000F; Wed, 5 Mar 2025 14:39:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 54667280008 for ; Wed, 5 Mar 2025 14:39:08 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 01AF81A077F for ; Wed, 5 Mar 2025 15:59:38 +0000 (UTC) X-FDA: 83187957678.06.25A1471 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf02.hostedemail.com (Postfix) with ESMTP id 91EDA80004 for ; Wed, 5 Mar 2025 15:59:35 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=cuebFD0f; dmarc=none; spf=none (imf02.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1741190377; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7Y2iYOEFpNWqetRFh3zM7CAI67w9Q6a6A/VNoZkwi3s=; b=mX0O8XvGkuDTT5HBnmoGf0qs94xzCQQ97ya0XEv3Nt25yPhOaw+J4a9JCrwZffwwFAqSBF y9pg7VVavTk59+5puGh/8b63tgbCAGAeiXTXgipSGvCroHRbLTO2awUqnQztrrhujqWT0I fox8+8aPKqvyb3PiUdBbF9zWHpMSH9k= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1741190377; a=rsa-sha256; cv=none; b=k9vA87Ejh5QRuztV1q/zJS/fjUlAAlB1fsIo7Zb8GiMqp6xJIaBGBBddtbLRouau7MsDa4 2ggbmc1lIocn2kGV3NYQHPMkYUhSzsFZC+U4yFYxnfOhUinZvaEvqdL+rKvp9cYEbbhIt8 0oI2TWFMAU2K2R6H47Tx7iL4DPyODJQ= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=cuebFD0f; dmarc=none; spf=none (imf02.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=7Y2iYOEFpNWqetRFh3zM7CAI67w9Q6a6A/VNoZkwi3s=; b=cuebFD0f3VLMeu0TXyDdxu1vVM U8gApbbelpc2C51zn9IG5PffrLZyy8/9L80Ok4B475uNs2O7F85ae8kVA5vhDMIXJT/YCDkO/N9sd MJaPV9rQ9F1c3TKkWM55Sc6hZRtZnLIP/Jl6EAB5JRLOQF+YD7MHr1Tf4IvwqaWiPpaBCKXcMA2ej yyvvrEaFCRS+fAlAfChk+1rUCovmf1Qxzyt/9p3N4/mCI32EAZ4hyzBuUBws8ri/82y/1aI9NIe26 kXVz5JAD23Zz5heneqv6Z9sIRvdRznU6oda9hymsTcdMfJHbIRJpOtcSoJDSaBPiTjDXt0NIVXBxV 4jVPjBPQ==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tpr9c-00000005oQd-46ye; Wed, 05 Mar 2025 15:59:29 +0000 Date: Wed, 5 Mar 2025 15:59:28 +0000 From: Matthew Wilcox To: Lorenzo Stoakes Cc: Andrew Morton , Vlastimil Babka , Jann Horn , "Liam R . Howlett" , Alexander Viro , Christian Brauner , Jan Kara , Paul Moore , Stephen Smalley , Ondrej Mosnacek , Suren Baghdasaryan , David Hildenbrand , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org Subject: Re: [RFC PATCH 0/2] mm: introduce anon_vma flags, reduce kernel allocs Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 91EDA80004 X-Stat-Signature: aa863c7ynm58an7p61ymzdx7phi9i7gj X-HE-Tag: 1741190375-21797 X-HE-Meta: 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 aTUTbR2J oFyRgoxGUF0SKIAyhgonYtyo6CF5gz5NTgphhoq4fjZtaDpJAxNFcZKWeRKYZHHDzgto/q2SaB14JQWJmDq9xOuLLrwUnUgxnbdqRSyVc9mrJVp/uWnIZP5De9djAbE1blIcdfBzIgIP7Tc2uqseeUzbNiXHvsjsDnF3hwiPK17gV5+dEAPUqumqZID7GTT5iNjOUSDQrLyeTbO533sKOWJm494dT9vIvgglCjEIf6UpihTcebhfkLZtr+zwWub9fs+H2Uj6GJ9R51O3CaptDzkvGbYPiLr8CQCfof3yMwdhAetliBAwkXAOXHkABQrMYL8YxHbjjzMTq0IkU2jnNiJi9i88CzPQFCRpm 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 Wed, Mar 05, 2025 at 02:55:06PM +0000, Lorenzo Stoakes wrote: > So adding additional fields is generally unviable, and VMA flags are > equally as contended, and prevent VMA merge, further impacting overhead. > > We can however make use of the time-honoured kernel tradition of grabbing > bits where we can. > > Since we can rely upon anon_vma allocations being at least system > word-aligned, we have a handful of bits in the vma->anon_vma available to > use as flags. I'm not a huge fan when there's a much better solution. It's an unsigned long, but we can only use the first 32 bits because of 32-bit compatibility? This is a noose we've made for our own neck. (there are many more places to fix up; this is illustrative): diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h index 0660a03d37d9..c6ea81ff4afe 100644 --- a/include/linux/hugetlb_inline.h +++ b/include/linux/hugetlb_inline.h @@ -8,7 +8,7 @@ static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma) { - return !!(vma->vm_flags & VM_HUGETLB); + return test_bit(VM_HUGETLB, vma->vm_flags); } #else diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 0ca9feec67b8..763210ba70b6 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -571,7 +571,8 @@ static inline void *folio_get_private(struct folio *folio) return folio->private; } -typedef unsigned long vm_flags_t; +#define VM_FLAGS_COUNT (8 / sizeof(unsigned long)) +typedef unsigned long vm_flags_t[VM_FLAGS_COUNT]; /* * A region containing a mapping of a non-memory backed file under NOMMU