From patchwork Thu Jun 11 19:44:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 280688 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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=ham 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 BCBA9C433DF for ; Thu, 11 Jun 2020 20:41:24 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 8696D2073E for ; Thu, 11 Jun 2020 20:41:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ipGBGsmv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8696D2073E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40424 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jjU0p-0007Q4-Nh for qemu-devel@archiver.kernel.org; Thu, 11 Jun 2020 16:41:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56208) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jjTAX-00026x-55 for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:47:21 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:51913 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jjTAP-0001Qm-Tg for qemu-devel@nongnu.org; Thu, 11 Jun 2020 15:47:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591904833; 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=zYBTb0M0ZA3DWZb/MQ7k4GbYqnZpIJsslP+QwLOSIHU=; b=ipGBGsmvcklcMn56ay1qUKvZQXMoZUwLYMLPnS804DUtzJwITSnv2GTAeeGI0txel3oQST qx0b0yzmQo0E0/dUszthJLarm+8yhzy+qb67iO2SCpH6ESXFIxgKipL9r7NShq1dXFXEY1 AXuI7UfrLxX/DcBYmh1AvfvslQYAf8Q= 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-43-HMnhUwunPMKZjlxQ9QCHJA-1; Thu, 11 Jun 2020 15:46:53 -0400 X-MC-Unique: HMnhUwunPMKZjlxQ9QCHJA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BC0E7107AD9A; Thu, 11 Jun 2020 19:46:46 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 43DA060CC0; Thu, 11 Jun 2020 19:46:46 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 073/115] replay: implement fair mutex Date: Thu, 11 Jun 2020 15:44:07 -0400 Message-Id: <20200611194449.31468-74-pbonzini@redhat.com> In-Reply-To: <20200611194449.31468-1-pbonzini@redhat.com> References: <20200611194449.31468-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=207.211.31.81; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/11 03:29:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pavel Dovgalyuk , Pavel Dovgalyuk Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Pavel Dovgalyuk In record/replay icount mode main loop thread and vCPU thread do not perform simultaneously. They take replay mutex to synchronize the actions. Sometimes vCPU thread waits for locking the mutex for very long time, because main loop releases the mutex and takes it back again. Standard qemu mutex do not provide the ordering capabilities. This patch adds a "queue" for replay mutex. Therefore thread ordering becomes more "fair". Threads are executed in the same order as they are trying to take the mutex. Signed-off-by: Pavel Dovgalyuk Message-Id: <158823802979.28101.9340462887738957616.stgit@pasha-ThinkPad-X280> Signed-off-by: Paolo Bonzini --- replay/replay-internal.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/replay/replay-internal.c b/replay/replay-internal.c index eba8246aae..2e8a3e947a 100644 --- a/replay/replay-internal.c +++ b/replay/replay-internal.c @@ -22,6 +22,9 @@ It also protects replay events queue which stores events to be written or read to the log. */ static QemuMutex lock; +/* Condition and queue for fair ordering of mutex lock requests. */ +static QemuCond mutex_cond; +static unsigned long mutex_head, mutex_tail; /* File for replay writing */ static bool write_error; @@ -197,9 +200,10 @@ static __thread bool replay_locked; void replay_mutex_init(void) { qemu_mutex_init(&lock); + qemu_cond_init(&mutex_cond); /* Hold the mutex while we start-up */ - qemu_mutex_lock(&lock); replay_locked = true; + ++mutex_tail; } bool replay_mutex_locked(void) @@ -211,10 +215,16 @@ bool replay_mutex_locked(void) void replay_mutex_lock(void) { if (replay_mode != REPLAY_MODE_NONE) { + unsigned long id; g_assert(!qemu_mutex_iothread_locked()); g_assert(!replay_mutex_locked()); qemu_mutex_lock(&lock); + id = mutex_tail++; + while (id != mutex_head) { + qemu_cond_wait(&mutex_cond, &lock); + } replay_locked = true; + qemu_mutex_unlock(&lock); } } @@ -222,7 +232,10 @@ void replay_mutex_unlock(void) { if (replay_mode != REPLAY_MODE_NONE) { g_assert(replay_mutex_locked()); + qemu_mutex_lock(&lock); + ++mutex_head; replay_locked = false; + qemu_cond_broadcast(&mutex_cond); qemu_mutex_unlock(&lock); } }