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[Qemu-devel] [RFC PATCH v3 15/30] cpus: push BQL lock to qemu_*_wait_io_
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] [RFC PATCH v3 15/30] cpus: push BQL lock to qemu_*_wait_io_event |
Date: |
Thu, 11 Jan 2018 11:26:21 +0300 |
User-agent: |
StGit/0.17.1-dirty |
From: Alex Bennée <address@hidden>
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 Bennée <address@hidden>
Tested-by: Pavel Dovgalyuk <address@hidden>
---
accel/kvm/kvm-all.c | 4 ----
cpus.c | 27 ++++++++++++++++++++-------
target/i386/hax-all.c | 2 --
3 files changed, 20 insertions(+), 13 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f290f48..8d1d2c4 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -1857,9 +1857,7 @@ int kvm_cpu_exec(CPUState *cpu)
return EXCP_HLT;
}
- qemu_mutex_unlock_iothread();
cpu_exec_start(cpu);
-
do {
MemTxAttrs attrs;
@@ -1989,8 +1987,6 @@ int kvm_cpu_exec(CPUState *cpu)
} while (ret == 0);
cpu_exec_end(cpu);
- qemu_mutex_lock_iothread();
-
if (ret < 0) {
cpu_dump_state(cpu, stderr, fprintf, CPU_DUMP_CODE);
vm_stop(RUN_STATE_INTERNAL_ERROR);
diff --git a/cpus.c b/cpus.c
index b4146a8..82dcbf8 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1149,6 +1149,8 @@ static bool qemu_tcg_should_sleep(CPUState *cpu)
static void qemu_tcg_wait_io_event(CPUState *cpu)
{
+ qemu_mutex_lock_iothread();
+
while (qemu_tcg_should_sleep(cpu)) {
stop_tcg_kick_timer();
qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
@@ -1157,15 +1159,21 @@ static void qemu_tcg_wait_io_event(CPUState *cpu)
start_tcg_kick_timer();
qemu_wait_io_event_common(cpu);
+
+ qemu_mutex_unlock_iothread();
}
static void qemu_kvm_wait_io_event(CPUState *cpu)
{
+ qemu_mutex_lock_iothread();
+
while (cpu_thread_is_idle(cpu)) {
qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
}
qemu_wait_io_event_common(cpu);
+
+ qemu_mutex_unlock_iothread();
}
static void qemu_hvf_wait_io_event(CPUState *cpu)
@@ -1199,6 +1207,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
/* signal CPU creation */
cpu->created = true;
+ qemu_mutex_unlock_iothread();
+
qemu_cond_signal(&qemu_cpu_cond);
do {
@@ -1241,10 +1251,10 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
/* signal CPU creation */
cpu->created = true;
+ qemu_mutex_unlock_iothread();
qemu_cond_signal(&qemu_cpu_cond);
while (1) {
- qemu_mutex_unlock_iothread();
do {
int sig;
r = sigwait(&waitset, &sig);
@@ -1255,6 +1265,7 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
}
qemu_mutex_lock_iothread();
qemu_wait_io_event_common(cpu);
+ qemu_mutex_unlock_iothread();
}
return NULL;
@@ -1343,11 +1354,9 @@ static int tcg_cpu_exec(CPUState *cpu)
#ifdef CONFIG_PROFILER
ti = profile_getclock();
#endif
- qemu_mutex_unlock_iothread();
cpu_exec_start(cpu);
ret = cpu_exec(cpu);
cpu_exec_end(cpu);
- qemu_mutex_lock_iothread();
#ifdef CONFIG_PROFILER
tcg_time += profile_getclock() - ti;
#endif
@@ -1407,6 +1416,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
qemu_wait_io_event_common(cpu);
}
}
+ qemu_mutex_unlock_iothread();
start_tcg_kick_timer();
@@ -1416,6 +1426,9 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
cpu->exit_request = 1;
while (1) {
+
+ qemu_mutex_lock_iothread();
+
/* Account partial waits to QEMU_CLOCK_VIRTUAL. */
qemu_account_warp_timer();
@@ -1424,6 +1437,8 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
*/
handle_icount_deadline();
+ qemu_mutex_unlock_iothread();
+
if (!cpu) {
cpu = first_cpu;
}
@@ -1449,9 +1464,7 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
cpu_handle_guest_debug(cpu);
break;
} else if (r == EXCP_ATOMIC) {
- qemu_mutex_unlock_iothread();
cpu_exec_step_atomic(cpu);
- qemu_mutex_lock_iothread();
break;
}
} else if (cpu->stop) {
@@ -1492,6 +1505,7 @@ static void *qemu_hax_cpu_thread_fn(void *arg)
current_cpu = cpu;
hax_init_vcpu(cpu);
+ qemu_mutex_unlock_iothread();
qemu_cond_signal(&qemu_cpu_cond);
while (1) {
@@ -1584,6 +1598,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
cpu->created = true;
cpu->can_do_io = 1;
current_cpu = cpu;
+ qemu_mutex_unlock_iothread();
qemu_cond_signal(&qemu_cpu_cond);
/* process any pending work */
@@ -1608,9 +1623,7 @@ 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;
diff --git a/target/i386/hax-all.c b/target/i386/hax-all.c
index 3ce6950..9fd60d9 100644
--- a/target/i386/hax-all.c
+++ b/target/i386/hax-all.c
@@ -513,11 +513,9 @@ static int hax_vcpu_hax_exec(CPUArchState *env)
hax_vcpu_interrupt(env);
- qemu_mutex_unlock_iothread();
cpu_exec_start(cpu);
hax_ret = hax_vcpu_run(vcpu);
cpu_exec_end(cpu);
- qemu_mutex_lock_iothread();
/* Simply continue the vcpu_run if system call interrupted */
if (hax_ret == -EINTR || hax_ret == -EAGAIN) {
- [Qemu-devel] [RFC PATCH v3 05/30] blkreplay: create temporary overlay for underlaying devices, (continued)
- [Qemu-devel] [RFC PATCH v3 05/30] blkreplay: create temporary overlay for underlaying devices, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 06/30] replay: disable default snapshot for record/replay, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 07/30] replay: fix processing async events, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 08/30] replay: fixed replay_enable_events, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 09/30] replay: fix save/load vm for non-empty queue, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 10/30] replay: added replay log format description, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 11/30] replay: make safe vmstop at record/replay, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 12/30] replay: save prior value of the host clock, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 13/30] icount: fixed saving/restoring of icount warp timers, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 14/30] target/arm/arm-powertctl: drop BQL assertions, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 15/30] cpus: push BQL lock to qemu_*_wait_io_event,
Pavel Dovgalyuk <=
- [Qemu-devel] [RFC PATCH v3 16/30] cpus: only take BQL for sleeping threads, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 17/30] replay/replay.c: bump REPLAY_VERSION again, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 18/30] replay/replay-internal.c: track holding of replay_lock, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 19/30] replay: make locking visible outside replay code, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 20/30] replay: push replay_mutex_lock up the call tree, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 21/30] replay: don't destroy mutex at exit, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 22/30] replay: check return values of fwrite, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 23/30] replay: avoid recursive call of checkpoints, Pavel Dovgalyuk, 2018/01/11
- [Qemu-devel] [RFC PATCH v3 24/30] scripts/qemu-gdb: add simple tcg lock status helper, Pavel Dovgalyuk, 2018/01/11