From patchwork Fri Feb 2 10:28:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 1894479 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=i+7kKx3c; dkim-atps=neutral Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=patchwork.ozlabs.org) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4TRBsd3C5Mz23g7 for ; Fri, 2 Feb 2024 21:32:05 +1100 (AEDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rVqp5-0001bF-60; Fri, 02 Feb 2024 05:31:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rVqoy-00018j-7r for qemu-devel@nongnu.org; Fri, 02 Feb 2024 05:30:58 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rVqov-00020m-Ni for qemu-devel@nongnu.org; Fri, 02 Feb 2024 05:30:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706869853; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QCMu/h0Uagcfb4ObsHyaNRe66JC3h0/VZ/U7Orz2xOU=; b=i+7kKx3ckhTOhNzCHix+P/Q8v2shZJKPNqhrif8/bGDFbM6iTz1iInWfZWGKYK21Uca0MU ySc29LaTFtim5jL65oGaRgGPT4aiyOL0AjX8xm4G2ieZWG8JM1QzSNsGFUVYiaYKw7Cm/m smIwLFYkyXSMwQZgNCyqui3okDt9IQk= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-260-hZP7jx5fNCCqUNBLQ28FHw-1; Fri, 02 Feb 2024 05:30:49 -0500 X-MC-Unique: hZP7jx5fNCCqUNBLQ28FHw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 58B973C0BE50; Fri, 2 Feb 2024 10:30:49 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3D5F740C9444; Fri, 2 Feb 2024 10:30:44 +0000 (UTC) From: peterx@redhat.com To: qemu-devel@nongnu.org Cc: Hao Xiang , Bryan Zhang , Fabiano Rosas , peterx@redhat.com, Avihai Horon , Yuan Liu , Prasad Pandit Subject: [PATCH v2 18/23] migration/multifd: Rewrite multifd_queue_page() Date: Fri, 2 Feb 2024 18:28:52 +0800 Message-ID: <20240202102857.110210-19-peterx@redhat.com> In-Reply-To: <20240202102857.110210-1-peterx@redhat.com> References: <20240202102857.110210-1-peterx@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.292, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Peter Xu The current multifd_queue_page() is not easy to read and follow. It is not good with a few reasons: - No helper at all to show what exactly does a condition mean; in short, readability is low. - Rely on pages->ramblock being cleared to detect an empty queue. It's slightly an overload of the ramblock pointer, per Fabiano [1], which I also agree. - Contains a self recursion, even if not necessary.. Rewrite this function. We add some comments to make it even clearer on what it does. [1] https://lore.kernel.org/r/87wmrpjzew.fsf@suse.de Signed-off-by: Peter Xu Reviewed-by: Fabiano Rosas --- migration/multifd.c | 56 ++++++++++++++++++++++++++++++--------------- 1 file changed, 37 insertions(+), 19 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index 35d4e8ad1f..4ab8e6eff2 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -506,35 +506,53 @@ static bool multifd_send_pages(void) return true; } +static inline bool multifd_queue_empty(MultiFDPages_t *pages) +{ + return pages->num == 0; +} + +static inline bool multifd_queue_full(MultiFDPages_t *pages) +{ + return pages->num == pages->allocated; +} + +static inline void multifd_enqueue(MultiFDPages_t *pages, ram_addr_t offset) +{ + pages->offset[pages->num++] = offset; +} + /* Returns true if enqueue successful, false otherwise */ bool multifd_queue_page(RAMBlock *block, ram_addr_t offset) { - MultiFDPages_t *pages = multifd_send_state->pages; - bool changed = false; + MultiFDPages_t *pages; + +retry: + pages = multifd_send_state->pages; - if (!pages->block) { + /* If the queue is empty, we can already enqueue now */ + if (multifd_queue_empty(pages)) { pages->block = block; + multifd_enqueue(pages, offset); + return true; } - if (pages->block == block) { - pages->offset[pages->num] = offset; - pages->num++; - - if (pages->num < pages->allocated) { - return true; + /* + * Not empty, meanwhile we need a flush. It can because of either: + * + * (1) The page is not on the same ramblock of previous ones, or, + * (2) The queue is full. + * + * After flush, always retry. + */ + if (pages->block != block || multifd_queue_full(pages)) { + if (!multifd_send_pages()) { + return false; } - } else { - changed = true; - } - - if (!multifd_send_pages()) { - return false; - } - - if (changed) { - return multifd_queue_page(block, offset); + goto retry; } + /* Not empty, and we still have space, do it! */ + multifd_enqueue(pages, offset); return true; }