From nobody Mon Oct 27 17:59:39 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1516698414867164.7054711755752; Tue, 23 Jan 2018 01:06:54 -0800 (PST) Received: from localhost ([::1]:46122 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eduXd-00045T-AI for importer@patchew.org; Tue, 23 Jan 2018 04:06:53 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40560) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eduLW-0001iJ-UE for qemu-devel@nongnu.org; Tue, 23 Jan 2018 03:54:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eduLV-0008Ux-Ix for qemu-devel@nongnu.org; Tue, 23 Jan 2018 03:54:23 -0500 Received: from mail.ispras.ru ([83.149.199.45]:57202) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eduLV-0008Ul-69 for qemu-devel@nongnu.org; Tue, 23 Jan 2018 03:54:21 -0500 Received: from [127.0.1.1] (unknown [85.142.117.226]) by mail.ispras.ru (Postfix) with ESMTPSA id 3DD8154006A; Tue, 23 Jan 2018 11:54:20 +0300 (MSK) From: Pavel Dovgalyuk To: qemu-devel@nongnu.org Date: Tue, 23 Jan 2018 11:54:21 +0300 Message-ID: <20180123085421.3419.45127.stgit@pasha-VirtualBox> In-Reply-To: <20180123085319.3419.97865.stgit@pasha-VirtualBox> References: <20180123085319.3419.97865.stgit@pasha-VirtualBox> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 83.149.199.45 Subject: [Qemu-devel] [RFC PATCH v5 11/24] cpus: push BQL lock to qemu_*_wait_io_event X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, pavel.dovgaluk@ispras.ru, mst@redhat.com, jasowang@redhat.com, quintela@redhat.com, zuban32s@gmail.com, maria.klimushenkova@ispras.ru, dovgaluk@ispras.ru, kraxel@redhat.com, boost.lists@gmail.com, pbonzini@redhat.com, alex.bennee@linaro.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 From: Alex Benn=C3=A9e We only really need to grab the lock for initial setup (so we don't race with the thread-spawning thread). After that we can drop the lock for the whole main loop and only grab it for waiting for IO events. There is a slight wrinkle for the round-robin TCG thread as we also expire timers which needs to be done under BQL as they are in the main-loop. This is stage one of reducing the lock impact as we can drop the requirement of implicit BQL for async work and only grab the lock when we need to sleep on the cpu->halt_cond. Signed-off-by: Alex Benn=C3=A9e Signed-off-by: Pavel Dovgalyuk --- accel/kvm/kvm-all.c | 1 - cpus.c | 29 +++++++++++++++++------------ 2 files changed, 17 insertions(+), 13 deletions(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 071f4f5..9628512 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -1863,7 +1863,6 @@ int kvm_cpu_exec(CPUState *cpu) =20 qemu_mutex_unlock_iothread(); cpu_exec_start(cpu); - do { MemTxAttrs attrs; =20 diff --git a/cpus.c b/cpus.c index 2cb0af9..577c764 100644 --- a/cpus.c +++ b/cpus.c @@ -1141,6 +1141,7 @@ static void qemu_wait_io_event_common(CPUState *cpu) =20 static void qemu_tcg_rr_wait_io_event(CPUState *cpu) { + qemu_mutex_lock_iothread(); while (all_cpu_threads_idle()) { stop_tcg_kick_timer(); qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex); @@ -1149,10 +1150,13 @@ static void qemu_tcg_rr_wait_io_event(CPUState *cpu) start_tcg_kick_timer(); =20 qemu_wait_io_event_common(cpu); + qemu_mutex_unlock_iothread(); } =20 static void qemu_wait_io_event(CPUState *cpu) { + qemu_mutex_lock_iothread(); + while (cpu_thread_is_idle(cpu)) { qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex); } @@ -1164,6 +1168,7 @@ static void qemu_wait_io_event(CPUState *cpu) } #endif qemu_wait_io_event_common(cpu); + qemu_mutex_unlock_iothread(); } =20 static void *qemu_kvm_cpu_thread_fn(void *arg) @@ -1189,6 +1194,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg) =20 /* signal CPU creation */ cpu->created =3D true; + qemu_mutex_unlock_iothread(); + qemu_cond_signal(&qemu_cpu_cond); =20 do { @@ -1204,7 +1211,6 @@ static void *qemu_kvm_cpu_thread_fn(void *arg) qemu_kvm_destroy_vcpu(cpu); cpu->created =3D false; qemu_cond_signal(&qemu_cpu_cond); - qemu_mutex_unlock_iothread(); return NULL; } =20 @@ -1231,10 +1237,10 @@ static void *qemu_dummy_cpu_thread_fn(void *arg) =20 /* signal CPU creation */ cpu->created =3D true; + qemu_mutex_unlock_iothread(); qemu_cond_signal(&qemu_cpu_cond); =20 while (1) { - qemu_mutex_unlock_iothread(); do { int sig; r =3D sigwait(&waitset, &sig); @@ -1243,7 +1249,6 @@ static void *qemu_dummy_cpu_thread_fn(void *arg) perror("sigwait"); exit(1); } - qemu_mutex_lock_iothread(); qemu_wait_io_event(cpu); } =20 @@ -1333,11 +1338,9 @@ static int tcg_cpu_exec(CPUState *cpu) #ifdef CONFIG_PROFILER ti =3D profile_getclock(); #endif - qemu_mutex_unlock_iothread(); cpu_exec_start(cpu); ret =3D cpu_exec(cpu); cpu_exec_end(cpu); - qemu_mutex_lock_iothread(); #ifdef CONFIG_PROFILER tcg_time +=3D profile_getclock() - ti; #endif @@ -1397,6 +1400,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) qemu_wait_io_event_common(cpu); } } + qemu_mutex_unlock_iothread(); =20 start_tcg_kick_timer(); =20 @@ -1406,6 +1410,8 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) cpu->exit_request =3D 1; =20 while (1) { + qemu_mutex_lock_iothread(); + /* Account partial waits to QEMU_CLOCK_VIRTUAL. */ qemu_account_warp_timer(); =20 @@ -1414,6 +1420,8 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) */ handle_icount_deadline(); =20 + qemu_mutex_unlock_iothread(); + if (!cpu) { cpu =3D first_cpu; } @@ -1439,9 +1447,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) cpu_handle_guest_debug(cpu); break; } else if (r =3D=3D EXCP_ATOMIC) { - qemu_mutex_unlock_iothread(); cpu_exec_step_atomic(cpu); - qemu_mutex_lock_iothread(); break; } } else if (cpu->stop) { @@ -1482,6 +1488,7 @@ static void *qemu_hax_cpu_thread_fn(void *arg) current_cpu =3D cpu; =20 hax_init_vcpu(cpu); + qemu_mutex_unlock_iothread(); qemu_cond_signal(&qemu_cpu_cond); =20 while (1) { @@ -1518,8 +1525,9 @@ static void *qemu_hvf_cpu_thread_fn(void *arg) =20 hvf_init_vcpu(cpu); =20 - /* signal CPU creation */ cpu->created =3D true; + qemu_mutex_unlock_iothread(); + /* signal CPU creation */ qemu_cond_signal(&qemu_cpu_cond); =20 do { @@ -1535,7 +1543,6 @@ static void *qemu_hvf_cpu_thread_fn(void *arg) hvf_vcpu_destroy(cpu); cpu->created =3D false; qemu_cond_signal(&qemu_cpu_cond); - qemu_mutex_unlock_iothread(); return NULL; } =20 @@ -1568,6 +1575,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) cpu->created =3D true; cpu->can_do_io =3D 1; current_cpu =3D cpu; + qemu_mutex_unlock_iothread(); qemu_cond_signal(&qemu_cpu_cond); =20 /* process any pending work */ @@ -1592,9 +1600,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) g_assert(cpu->halted); break; case EXCP_ATOMIC: - qemu_mutex_unlock_iothread(); cpu_exec_step_atomic(cpu); - qemu_mutex_lock_iothread(); default: /* Ignore everything else? */ break; @@ -1603,7 +1609,6 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) qemu_tcg_destroy_vcpu(cpu); cpu->created =3D false; qemu_cond_signal(&qemu_cpu_cond); - qemu_mutex_unlock_iothread(); return NULL; } =20