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 42743C38142 for ; Fri, 27 Jan 2023 22:52:42 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4P3XsN5DVKz3fJ8 for ; Sat, 28 Jan 2023 09:52:40 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=xdl9dDNi; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux-foundation.org (client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=akpm@linux-foundation.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=xdl9dDNi; dkim-atps=neutral Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4P3XrK6H83z3fGk for ; Sat, 28 Jan 2023 09:51:44 +1100 (AEDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7634F61DD4; Fri, 27 Jan 2023 22:51:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D9C1C433D2; Fri, 27 Jan 2023 22:51:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1674859900; bh=IS6HJYpOFVi4CPNNzsDzDEh+FBChpu2Srs6gQMB3T7c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=xdl9dDNiVfKw9plbtOCSZ3wgAXFIUPm0+vCYThT9kkVXydC3Lpt4rCbsKFSpmh5J6 xhw22O9gnJ3RCXD8MMY2pf3uVqv2FVCAMMyU94nKeibSdmQ1nrUKmVGl402SKKokDs C4VaPgO8KEB+Pk7caieUiDgaDjEAhyGy9DYMnZ7o= Date: Fri, 27 Jan 2023 14:51:38 -0800 From: Andrew Morton To: Suren Baghdasaryan Subject: Re: [PATCH v2 00/33] Per-VMA locks Message-Id: <20230127145138.8cc44bf00ebf289dffec0975@linux-foundation.org> In-Reply-To: <20230127194110.533103-1-surenb@google.com> References: <20230127194110.533103-1-surenb@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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, dave@stgolabs.net, minchan@google.com, x86@kernel.org, hughd@google.com, willy@infradead.org, gurua@google.com, mingo@redhat.com, linux-arm-kernel@lists.infradead.org, rientjes@google.com, axelrasmussen@google.com, kernel-team@android.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, tatashin@google.com, mgorman@techsingularity.net, rppt@kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, 27 Jan 2023 11:40:37 -0800 Suren Baghdasaryan wrote: > Per-vma locks idea that was discussed during SPF [1] discussion at LSF/MM > last year [2], which concluded with suggestion that “a reader/writer > semaphore could be put into the VMA itself; that would have the effect of > using the VMA as a sort of range lock. There would still be contention at > the VMA level, but it would be an improvement.” This patchset implements > this suggested approach. I think I'll await reviewer/tester input for a while. > The patchset implements per-VMA locking only for anonymous pages which > are not in swap and avoids userfaultfs as their implementation is more > complex. Additional support for file-back page faults, swapped and user > pages can be added incrementally. This is a significant risk. How can we be confident that these as yet unimplemented parts are implementable and that the result will be good?