From patchwork Sat May 7 01:57:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Leonardo Bras X-Patchwork-Id: 12841813 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.gnu.org (lists.gnu.org [209.51.188.17]) (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 CFE78C433F5 for ; Sat, 7 May 2022 02:03:55 +0000 (UTC) Received: from localhost ([::1]:56366 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nn9nX-0005o5-0R for qemu-devel@archiver.kernel.org; Fri, 06 May 2022 22:03:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43770) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nn9if-0005gM-NO for qemu-devel@nongnu.org; Fri, 06 May 2022 21:58:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59258) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nn9ie-0006jp-4c for qemu-devel@nongnu.org; Fri, 06 May 2022 21:58:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651888731; 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=nKIqzXZ0u4hsOAjTKtMqbZ1MW0BdUgNP96TObuznd/M=; b=a1QBn6YpnL6oQEI+EimjkrcgFXoChYEHdEsQMkxEzwG7KXEdbll8uGk5zG7thE59A7dUtZ VTuXisZzbgYJYiyaQRuC6/nUDWdFR6ufXV9Ys7qGNef+pTw2GWCMSxgX9Bm6aH5QrbGC39 rgw7ZKbgLgyuEUhTcaYjsPUSwvm01Yc= Received: from mail-ot1-f69.google.com (mail-ot1-f69.google.com [209.85.210.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-206-YgHpQPoGMcmo04wUD_CukA-1; Fri, 06 May 2022 21:58:50 -0400 X-MC-Unique: YgHpQPoGMcmo04wUD_CukA-1 Received: by mail-ot1-f69.google.com with SMTP id 64-20020a9d0346000000b00605ddf8273aso3592851otv.11 for ; Fri, 06 May 2022 18:58:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=nKIqzXZ0u4hsOAjTKtMqbZ1MW0BdUgNP96TObuznd/M=; b=itVTlZuKi3fHN9ZX/mJHtayo5YL5pmXl9T2qQU8am5be2o/donfa6MRE3gEDTJpxsw f2gzaKdQDolC71RpQSJv47q8huzZOFJFvMhf909DcY3BhS0OpmDtBmkYmu5PSY0YqouX QaTtzt5P3AHQIjUtoKtj2EwxM31dh+GMc6sz6iK8MB25tIWFPMCAwyIuPDgSCm92+lyu 4rU8H/wJYz6lrObt4OWVV4ymU8gojOoBtjDhzhU3G9adTzS1Laen8XqPt5t/o5O3gPxY Nln8AmWQ1QbUlp0a7JraYJ7UCz/sU1hw8LD37vl+DDDQsw2n26Rh/KwHH7+8e9/Ad1+Z E96Q== X-Gm-Message-State: AOAM53356QydaNEtQUH7OUqroHR/clg9aqelWM7LvTtWfx51mzeIzXCY mVRl1JtoIrbHI5//lzaXAvys+v+H9quKKuolMgSI0yBfDG7jixL/xEuu/RZacXLrFNvilXgXVYi v4lC+GvF1zsmcdmQ= X-Received: by 2002:a05:6808:3082:b0:326:9043:a8de with SMTP id bl2-20020a056808308200b003269043a8demr2611870oib.239.1651888729449; Fri, 06 May 2022 18:58:49 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyGL543lnXlG54bZrxgkuDbHQCaPlwDSw19nuVu+6969squx3fijvvPnWEVPe9WF8PpjSjYyw== X-Received: by 2002:a05:6808:3082:b0:326:9043:a8de with SMTP id bl2-20020a056808308200b003269043a8demr2611864oib.239.1651888729242; Fri, 06 May 2022 18:58:49 -0700 (PDT) Received: from localhost.localdomain ([2804:431:c7f0:55e:b3e6:9ebe:4b75:fe72]) by smtp.gmail.com with ESMTPSA id v18-20020a056830141200b0060603221281sm2218124otp.81.2022.05.06.18.58.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 May 2022 18:58:48 -0700 (PDT) From: Leonardo Bras To: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , Elena Ufimtseva , Jagannathan Raman , John G Johnson , =?utf-8?q?Daniel_P=2E_Berrang?= =?utf-8?q?=C3=A9?= , Juan Quintela , "Dr. David Alan Gilbert" , Eric Blake , Markus Armbruster , Fam Zheng , Peter Xu Cc: Leonardo Bras , qemu-devel@nongnu.org, qemu-block@nongnu.org Subject: [PATCH v12 6/7] multifd: Send header packet without flags if zero-copy-send is enabled Date: Fri, 6 May 2022 22:57:58 -0300 Message-Id: <20220507015759.840466-7-leobras@redhat.com> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220507015759.840466-1-leobras@redhat.com> References: <20220507015759.840466-1-leobras@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=170.10.133.124; envelope-from=leobras@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Since d48c3a0445 ("multifd: Use a single writev on the send side"), sending the header packet and the memory pages happens in the same writev, which can potentially make the migration faster. Using channel-socket as example, this works well with the default copying mechanism of sendmsg(), but with zero-copy-send=true, it will cause the migration to often break. This happens because the header packet buffer gets reused quite often, and there is a high chance that by the time the MSG_ZEROCOPY mechanism get to send the buffer, it has already changed, sending the wrong data and causing the migration to abort. It means that, as it is, the buffer for the header packet is not suitable for sending with MSG_ZEROCOPY. In order to enable zero copy for multifd, send the header packet on an individual write(), without any flags, and the remanining pages with a writev(), as it was happening before. This only changes how a migration with zero-copy-send=true works, not changing any current behavior for migrations with zero-copy-send=false. Signed-off-by: Leonardo Bras Reviewed-by: Peter Xu Reviewed-by: Daniel P. Berrangé --- migration/multifd.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index 15fb668e64..2541cd2322 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -617,6 +617,7 @@ static void *multifd_send_thread(void *opaque) MultiFDSendParams *p = opaque; Error *local_err = NULL; int ret = 0; + bool use_zero_copy_send = migrate_use_zero_copy_send(); trace_multifd_send_thread_start(p->id); rcu_register_thread(); @@ -639,9 +640,14 @@ static void *multifd_send_thread(void *opaque) if (p->pending_job) { uint64_t packet_num = p->packet_num; uint32_t flags = p->flags; - p->iovs_num = 1; p->normal_num = 0; + if (use_zero_copy_send) { + p->iovs_num = 0; + } else { + p->iovs_num = 1; + } + for (int i = 0; i < p->pages->num; i++) { p->normal[p->normal_num] = p->pages->offset[i]; p->normal_num++; @@ -665,8 +671,18 @@ static void *multifd_send_thread(void *opaque) trace_multifd_send(p->id, packet_num, p->normal_num, flags, p->next_packet_size); - p->iov[0].iov_len = p->packet_len; - p->iov[0].iov_base = p->packet; + if (use_zero_copy_send) { + /* Send header first, without zerocopy */ + ret = qio_channel_write_all(p->c, (void *)p->packet, + p->packet_len, &local_err); + if (ret != 0) { + break; + } + } else { + /* Send header using the same writev call */ + p->iov[0].iov_len = p->packet_len; + p->iov[0].iov_base = p->packet; + } ret = qio_channel_writev_all(p->c, p->iov, p->iovs_num, &local_err);