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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D20D2C4332F for ; Fri, 9 Dec 2022 14:40:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229521AbiLIOkf (ORCPT ); Fri, 9 Dec 2022 09:40:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229793AbiLIOka (ORCPT ); Fri, 9 Dec 2022 09:40:30 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 077E21B9C1 for ; Fri, 9 Dec 2022 06:39:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670596776; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=qCeskwiHpWOAgomtB/9x1S3AV/0GyFM2DFyZzy0TWI4=; b=IrVqmfvAdNitqZt5h1jOSDeuJ3EQTmBd6LqCCsZDKvpZIsB/6Tn4ZJmnK8PoMrk8RqD3TB zCw7FQyiwukpKWpduC/+51NVNCDVxepxFPeFVPCLUNzMUtXepYgoYM+patR93wbQgqXbtQ J4WoGOOUdKE9JGRw1PHD9msM1b2nl9s= Received: from mail-yb1-f199.google.com (mail-yb1-f199.google.com [209.85.219.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-583-6RYmbQuEPDK3u-gNNw3p8A-1; Fri, 09 Dec 2022 09:39:35 -0500 X-MC-Unique: 6RYmbQuEPDK3u-gNNw3p8A-1 Received: by mail-yb1-f199.google.com with SMTP id e15-20020a5b0ccf000000b006ed1704b40cso5132612ybr.5 for ; Fri, 09 Dec 2022 06:39:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=qCeskwiHpWOAgomtB/9x1S3AV/0GyFM2DFyZzy0TWI4=; b=Hf0pPGfJ47oz0OqujmLB2VcsWHgjCd4GarFH6elt0P520eegYbcw0YRXdizDL8CoNQ s1AZES6LdNCe5g8wbABjim/s8FoBIOgc2u6MNGYAnER2tvZw80ZuDAuH2LM8prPfnTGV XWOf1DTQSeFAh5NACSzsPLbWoyyobmRMJPvF6qaJBnqGEFHmd1UDm05jZ37hzbjoUVGC EGOqQhaAvjq5J6Yj9/QuAuZjjzqd2HSYERnt9SzJRPLyX9b4sN1TUscuIWv3Hhv8fh9I UEucNH/i/CxJGkHwRywXPLe/uIldPwTDEiHD0zZVkvV+i8uOyB0+24EamQUXviCNT9Bt ge5A== X-Gm-Message-State: ANoB5pmob8zvb0GvfUnOe4F/Oa5J7gvlziEqCpONye9rJXNh4TzMK5cB Owmxwm+cyVfJyLc6wKuJoW3WNLP1RSZHSTwBEAHjaRaDwRBzvc3QDgBNXPjDwniZOBTGj40dx8m 4YACNNc+MgsBWOvDgMk07fskh X-Received: by 2002:a05:7500:53d1:b0:ea:ada0:1fd5 with SMTP id y17-20020a05750053d100b000eaada01fd5mr362423gab.33.1670596774526; Fri, 09 Dec 2022 06:39:34 -0800 (PST) X-Google-Smtp-Source: AA0mqf6/0nCQ5bt3gKHOC8oSlO0XyXnR156+Xc0b03y9Hj9KtBO5tqL462ejhQMdh3cJRGFz31dx9w== X-Received: by 2002:a05:7500:53d1:b0:ea:ada0:1fd5 with SMTP id y17-20020a05750053d100b000eaada01fd5mr362409gab.33.1670596774162; Fri, 09 Dec 2022 06:39:34 -0800 (PST) Received: from x1n (bras-base-aurron9127w-grc-46-70-31-27-79.dsl.bell.ca. [70.31.27.79]) by smtp.gmail.com with ESMTPSA id m11-20020a05620a290b00b006e702033b15sm1275350qkp.66.2022.12.09.06.39.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Dec 2022 06:39:32 -0800 (PST) Date: Fri, 9 Dec 2022 09:39:30 -0500 From: Peter Xu To: David Hildenbrand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , John Hubbard , Andrea Arcangeli , James Houghton , Jann Horn , Rik van Riel , Miaohe Lin , Andrew Morton , Mike Kravetz , Nadav Amit Subject: Re: [PATCH v2 08/10] mm/hugetlb: Make walk_hugetlb_range() safe to pmd unshare Message-ID: References: <20221207203034.650899-1-peterx@redhat.com> <20221207203034.650899-9-peterx@redhat.com> <72a62bf5-7633-f35f-75fd-0222fd0ab49f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <72a62bf5-7633-f35f-75fd-0222fd0ab49f@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 09, 2022 at 11:24:55AM +0100, David Hildenbrand wrote: > For such cases, it would be good to have any evidence that it really helps. I don't know much on the s390 path, but if a process has a large hugetlb vma, even MADV_DONTNEED will be blocked for whatever long time if there's another process or thread scanning pagemap for this vma. Would this justify a bit? It's just that the vma lock is taken write far more than mmap_lock taken write I think, meanwhile what we need here is only release the lock and retake, nothing else. It didn't make things over complicated, IMO. No strong ipinion from my side, as I said to me it's really low hanging fruit. If you still think that doesn't justify and if Mike doesn't have a preference either I can just drop it for later. -- Peter Xu