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 X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48EE1C4363A for ; Fri, 16 Oct 2020 09:18:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A878720848 for ; Fri, 16 Oct 2020 09:18:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fmT9sYL1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A878720848 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1A5E794000A; Fri, 16 Oct 2020 05:18:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 157AE900002; Fri, 16 Oct 2020 05:18:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 01D2694000A; Fri, 16 Oct 2020 05:18:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0024.hostedemail.com [216.40.44.24]) by kanga.kvack.org (Postfix) with ESMTP id DDEB2900002 for ; Fri, 16 Oct 2020 05:18:51 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 99A8B181AEF10 for ; Fri, 16 Oct 2020 09:18:51 +0000 (UTC) X-FDA: 77377238862.25.bikes45_3712a322721b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id 752661804E3A1 for ; Fri, 16 Oct 2020 09:18:51 +0000 (UTC) X-HE-Tag: bikes45_3712a322721b X-Filterd-Recvd-Size: 5009 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Fri, 16 Oct 2020 09:18:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602839930; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rkDAPJVLLNu9aqbT2ZGJGKmJO7QPtcaA3nJyCliA/rs=; b=fmT9sYL1QPQlM4RrB7uRQuMMApST3JWpVuYtXHi+E/fEQD/R2KeVAVW239juZF2xf+Uu6w HvgRhf6yX5EqwEyXimriXGtqcEgW+y17KAkM5rwV75vDFCFo9dF18iZaGh581WYREfoVQS aEcPZyELakWSDZn5n7wGfh7MBn6ExrA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-494-N2dJj4zyMFWma92NUVlemw-1; Fri, 16 Oct 2020 05:18:46 -0400 X-MC-Unique: N2dJj4zyMFWma92NUVlemw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2142284BA66; Fri, 16 Oct 2020 09:18:45 +0000 (UTC) Received: from [10.36.113.23] (ovpn-113-23.ams2.redhat.com [10.36.113.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 817366EF70; Fri, 16 Oct 2020 09:18:40 +0000 (UTC) Subject: Re: [PATCH v1 09/29] virtio-mem: don't always trigger the workqueue when offlining memory To: Wei Yang Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org, Andrew Morton , "Michael S . Tsirkin" , Jason Wang , Pankaj Gupta References: <20201012125323.17509-1-david@redhat.com> <20201012125323.17509-10-david@redhat.com> <20201016040301.GJ86495@L-31X9LVDL-1304.local> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <82afba4e-66e2-ce05-c092-267301b66de9@redhat.com> Date: Fri, 16 Oct 2020 11:18:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201016040301.GJ86495@L-31X9LVDL-1304.local> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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: On 16.10.20 06:03, Wei Yang wrote: > On Mon, Oct 12, 2020 at 02:53:03PM +0200, David Hildenbrand wrote: >> Let's trigger from offlining code when we're not allowed to touch online >> memory. > > This describes the change in virtio_mem_memory_notifier_cb()? Ah, yes, can try to make that clearer. > >> >> Handle the other case (memmap possibly freeing up another memory block) >> when actually removing memory. When removing via virtio_mem_remove(), >> virtio_mem_retry() is a NOP and safe to use. >> >> While at it, move retry handling when offlining out of >> virtio_mem_notify_offline(), to share it with Device Block Mode (DBM) >> soon. > > I may not understand the logic fully. Here is my understanding of current > logic: > > > virtio_mem_run_wq() > virtio_mem_unplug_request() > virtio_mem_mb_unplug_any_sb_offline() > virtio_mem_mb_remove() --- 1 > virtio_mem_mb_unplug_any_sb_online() > virtio_mem_mb_offline_and_remove() --- 2 > > This patch tries to trigger the wq at 1 and 2. And these two functions are > only valid during this code flow. Exactly. > > These two functions actually remove some memory from the system. So I am not > sure where extra unplug-able memory comes from. I guess those memory is from > memory block device and mem_sectioin, memmap? While those memory is still > marked as online, right? Imagine you end up (only after some repeating plugging and unplugging of memory, otherwise it's obviously impossible): Memory block X: Contains only movable data Memory block X + 1: Contains memmap of Memory block X: We start to unplug from high, to low. 1. Try to unplug/offline/remove block X + 1: fails, because of the memmap 2. Try to unplug/offline/remove block X: succeeds. 3. Not all requested memory got unplugged. Sleep for 30 seconds. 4. Retry to unplug/offline/remove block X + 1: succeeds What we do in 2, is that we trigger a retry of ourselves. That means, that in 3. we don't actually sleep, but retry immediately. This has been proven helpful in some of my tests, where you want to unplug *a lot* of memory again, not just some parts. Triggering a retry is fairly cheap. Assume you don't actually have to perform any more unplugging. The workqueue wakes up, detects that nothing is to do, and goes back to sleep. -- Thanks, David / dhildenb