From patchwork Wed Jul 17 05:46:55 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicholas Piggin X-Patchwork-Id: 11047173 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 24C2913BD for ; Wed, 17 Jul 2019 05:47:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 12D5E286C6 for ; Wed, 17 Jul 2019 05:47:23 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 06B1B28708; Wed, 17 Jul 2019 05:47:23 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=2.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 90620286C6 for ; Wed, 17 Jul 2019 05:47:22 +0000 (UTC) Received: from localhost ([::1]:54216 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hncmf-0000BA-Aj for patchwork-qemu-devel@patchwork.kernel.org; Wed, 17 Jul 2019 01:47:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52133) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hncmV-00087Z-6J for qemu-devel@nongnu.org; Wed, 17 Jul 2019 01:47:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hncmU-0001ZK-23 for qemu-devel@nongnu.org; Wed, 17 Jul 2019 01:47:11 -0400 Received: from mail-pl1-x641.google.com ([2607:f8b0:4864:20::641]:36655) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hncmR-0001Xj-PA; Wed, 17 Jul 2019 01:47:07 -0400 Received: by mail-pl1-x641.google.com with SMTP id k8so11359865plt.3; Tue, 16 Jul 2019 22:47:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=d6z/VFzkc+E+tzTM4giE0MZX0TDQpyGL1Wz1LFCmAss=; b=G5U+ctfYpc04Oet4Stpr8F6vFjeP+LxpWMq4p5ZAfhfBr2jRZGTrA5Yw9l8+Mfighd taobcPlBzw2RsOt+AY98+lK/Y0LesqBlcxsJqj/hK3GocD7jRpLjSs9DkoZLIPutSsN9 9dl7AD7WuaRksseTzcbKaHo97uRbrgICFVFL+kcRrcVippETaZnUGp7qus+4uV6WJFN6 5bLudQfwQnG2iH4SJFeB1kP5Lz7EBzqvL5uU46fB+NZrZBGRY7/mXRomZ1Ee/PMpZmhE 820WNu9t1KeLSh9Vn2YLJq/IJApXo4YqohLcx9+xMx0nmXqVvglWNMd/Jfs9w4D7Thbx YEdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=d6z/VFzkc+E+tzTM4giE0MZX0TDQpyGL1Wz1LFCmAss=; b=iHOd1QRbAbGKG2FcHDueVrB/6r8dxFX4rRrT8it3X7D8shYRi7fRO87eIBnpu4Q2pd 5UldRnp1wI2YxvxNDw4RZpJ/S/BRv07V5/gFNqWdHWx9qeeb/xCq0WFUnRVI4544fs1i 5Pd1+S00tMpu8fedi4WMxI44hKd8Pvc55UMG89jJpUW4R9BEbWQ7g68rvqPkI8hP0gvU +/pedQvzAumhMGog7+68PxlOK8euvDYTqpzE75VBgCuymmKtZ8uaIXIAcGtLKdupwP2C 2deSnRiQf88m2rgqx3mjZPLIiqcyXvtGSpAyYbPjjVF2UjalgHsmiQkO9pGIXnZ77OjK BHeg== X-Gm-Message-State: APjAAAX68X2JEd6n4Wr1cqK1MJQcybG3EPrq4TfaHGXfQhfqGZs0ZCZ/ GvHNbkwxLwktXKIg4+cwS+g= X-Google-Smtp-Source: APXvYqx17i0Rz0TxdUrFmrmgxQR4qtPZGFQMUiFnrcXoEg1pYDAYTqWEdHeYrxwcy6w6l+km/PGf/w== X-Received: by 2002:a17:902:1566:: with SMTP id b35mr42000558plh.147.1563342426748; Tue, 16 Jul 2019 22:47:06 -0700 (PDT) Received: from bobo.local0.net ([203.220.8.141]) by smtp.gmail.com with ESMTPSA id q69sm32573165pjb.0.2019.07.16.22.47.02 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 16 Jul 2019 22:47:06 -0700 (PDT) From: Nicholas Piggin To: David Gibson Date: Wed, 17 Jul 2019 15:46:55 +1000 Message-Id: <20190717054655.14104-1-npiggin@gmail.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::641 Subject: [Qemu-devel] [RFC PATCH] Implement qemu_thread_yield for posix, use it in mttcg to handle EXCP_YIELD 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: Greg Kurz , Nicholas Piggin , qemu-devel@nongnu.org, qemu-ppc@nongnu.org, =?utf-8?q?C=C3=A9dric_Le_Goater?= Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP This is a bit of proof of concept in case mttcg becomes more important yield could be handled like this. You can have by accident or deliberately force vCPUs onto the same physical CPU and cause inversion issues when the lock holder was preempted by the waiter. This is lightly tested but not to the point of measuring performance difference. I really consider the previous confer/prod patches more important just to provide a more complete guest environment and better test coverage, than performance, but maybe someone wants to persue this. Thanks, Nick --- cpus.c | 6 ++++++ hw/ppc/spapr_hcall.c | 14 +++++++------- include/qemu/thread.h | 1 + util/qemu-thread-posix.c | 5 +++++ util/qemu-thread-win32.c | 4 ++++ 5 files changed, 23 insertions(+), 7 deletions(-) diff --git a/cpus.c b/cpus.c index 927a00aa90..f036e062d9 100644 --- a/cpus.c +++ b/cpus.c @@ -1760,6 +1760,12 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) qemu_mutex_unlock_iothread(); cpu_exec_step_atomic(cpu); qemu_mutex_lock_iothread(); + break; + case EXCP_YIELD: + qemu_mutex_unlock_iothread(); + qemu_thread_yield(); + qemu_mutex_lock_iothread(); + break; default: /* Ignore everything else? */ break; diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c index 57c1ee0fe1..9c24a64dfe 100644 --- a/hw/ppc/spapr_hcall.c +++ b/hw/ppc/spapr_hcall.c @@ -1162,13 +1162,13 @@ static target_ulong h_confer(PowerPCCPU *cpu, SpaprMachineState *spapr, return H_SUCCESS; } - /* - * The targeted confer does not do anything special beyond yielding - * the current vCPU, but even this should be better than nothing. - * At least for single-threaded tcg, it gives the target a chance to - * run before we run again. Multi-threaded tcg does not really do - * anything with EXCP_YIELD yet. - */ + /* + * The targeted confer does not do anything special beyond yielding + * the current vCPU, but even this should be better than nothing. + * For single-threaded tcg, it gives the target a chance to run + * before we run again, multi-threaded tcg will yield the CPU to + * another vCPU. + */ } cs->exception_index = EXCP_YIELD; diff --git a/include/qemu/thread.h b/include/qemu/thread.h index 55d83a907c..8525b0a70a 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -160,6 +160,7 @@ void qemu_thread_get_self(QemuThread *thread); bool qemu_thread_is_self(QemuThread *thread); void qemu_thread_exit(void *retval); void qemu_thread_naming(bool enable); +void qemu_thread_yield(void); struct Notifier; /** diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index 1bf5e65dea..91b12a1082 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -573,3 +573,8 @@ void *qemu_thread_join(QemuThread *thread) } return ret; } + +void qemu_thread_yield(void) +{ + pthread_yield(); +} diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c index 572f88535d..72fe406bef 100644 --- a/util/qemu-thread-win32.c +++ b/util/qemu-thread-win32.c @@ -442,3 +442,7 @@ bool qemu_thread_is_self(QemuThread *thread) { return GetCurrentThreadId() == thread->tid; } + +void qemu_thread_yield(void) +{ +}