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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7B859C61DA4 for ; Thu, 16 Feb 2023 15:46:48 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4PHfSk6ttQz3f3x for ; Fri, 17 Feb 2023 02:46:46 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=v4Efi6nP; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=infradead.org (client-ip=2001:8b0:10b:1236::1; helo=casper.infradead.org; envelope-from=willy@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=v4Efi6nP; dkim-atps=neutral Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4PHfRf247dz3bgj for ; Fri, 17 Feb 2023 02:45:50 +1100 (AEDT) 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=vKirnekWaY/7YPqBImOqS8So3dx7/6DOy0i+rRDyZWU=; b=v4Efi6nPZA8YmfeKqb5WLenlFD 0k/p7dZ0EdA4YcHjqljvXqOOGSthJzq++39zRp6/q2Fu4rML04k+dAt34kXAqraSx5+SMXuzcqQsy UqRfvsgKz+ns+xawbSRrvEqH2FL8wQw/a2euo4DuP0kKao3/m6HUeqG2HOLFnEz+essxCs3IK9fMo uXzSIf1j9gWIzAaDkTPeMbpnqt2dAqsOp5NQ2VRixq/5jMSgTzhQAV/Ozc5SeckJizTH65WZjobHc GsL2aTYFqint8RVP1arhPmGAA0U8cD3Uk++dP8hyMS3q3LIFjgWduyiTqRr6+sS5D3YudYdBxBLRG 3NhSq/pQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSgRD-008WXZ-IG; Thu, 16 Feb 2023 15:44:47 +0000 Date: Thu, 16 Feb 2023 15:44:47 +0000 From: Matthew Wilcox To: Suren Baghdasaryan Subject: Re: [PATCH v3 26/35] mm: fall back to mmap_lock if vma->anon_vma is not yet set Message-ID: References: <20230216051750.3125598-1-surenb@google.com> <20230216051750.3125598-27-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230216051750.3125598-27-surenb@google.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: michel@lespinasse.org, joelaf@google.com, songliubraving@fb.com, mhocko@suse.com, leewalsh@google.com, david@redhat.com, peterz@infradead.org, bigeasy@linutronix.de, peterx@redhat.com, dhowells@redhat.com, linux-mm@kvack.org, edumazet@google.com, jglisse@google.com, punit.agrawal@bytedance.com, will@kernel.org, arjunroy@google.com, chriscli@google.com, dave@stgolabs.net, minchan@google.com, x86@kernel.org, hughd@google.com, gurua@google.com, mingo@redhat.com, linux-arm-kernel@lists.infradead.org, rientjes@google.com, axelrasmussen@google.com, kernel-team@android.com, michalechner92@googlemail.com, soheil@google.com, paulmck@kernel.org, jannh@google.com, liam.howlett@oracle.com, shakeelb@google.com, luto@kernel.org, gthelen@google.com, ldufour@linux.ibm.com, vbabka@suse.cz, posk@google.com, lstoakes@gmail.com, peterjung1337@gmail.com, linuxppc-dev@lists.ozlabs.org, kent.overstreet@linux.dev, linux-kernel@vger.kernel.org, hannes@cmpxchg.org, akpm@linux-foundation.org, tatashin@goog le.com, mgorman@techsingularity.net, rppt@kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Feb 15, 2023 at 09:17:41PM -0800, Suren Baghdasaryan wrote: > When vma->anon_vma is not set, page fault handler will set it by either > reusing anon_vma of an adjacent VMA if VMAs are compatible or by > allocating a new one. find_mergeable_anon_vma() walks VMA tree to find > a compatible adjacent VMA and that requires not only the faulting VMA > to be stable but also the tree structure and other VMAs inside that tree. > Therefore locking just the faulting VMA is not enough for this search. > Fall back to taking mmap_lock when vma->anon_vma is not set. This > situation happens only on the first page fault and should not affect > overall performance. I think I asked this before, but don't remember getting an aswer. Why do we defer setting anon_vma to the first fault? Why don't we set it up at mmap time?