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[Qemu-devel] [RFC v1 08/11] tcg: add kick timer for single-threaded vCPU
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC v1 08/11] tcg: add kick timer for single-threaded vCPU emulation |
Date: |
Fri, 18 Mar 2016 16:18:49 +0000 |
Currently we rely on the side effect of the main loop grabbing the
iothread_mutex to give any long running basic block chains a kick to
ensure the next vCPU is scheduled. As this code is being re-factored and
rationalised we now do it explicitly here.
Signed-off-by: Alex Bennée <address@hidden>
---
cpus.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/cpus.c b/cpus.c
index 76bd321..a87fbf9 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1145,11 +1145,30 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
#endif
}
+/* Single-threaded TCG
+ *
+ * In the single-threaded case each vCPU is simulated in turn. If
+ * there is more than a single vCPU we create a simple timer to kick
+ * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
+ * This is done explicitly rather than relying on side-effects
+ * elsewhere.
+ */
static int tcg_cpu_exec(CPUState *cpu);
+static void qemu_cpu_kick_no_halt(void);
+
+static void kick_tcg_thread(void *opaque)
+{
+ QEMUTimer *self = *(QEMUTimer **) opaque;
+ timer_mod(self,
+ qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+ get_ticks_per_sec() / 10);
+ qemu_cpu_kick_no_halt();
+}
static void *qemu_tcg_cpu_thread_fn(void *arg)
{
CPUState *cpu = arg;
+ QEMUTimer *kick_timer;
rcu_register_thread();
@@ -1173,6 +1192,14 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
}
}
+ /* Set to kick if we have to do more than one vCPU */
+ if (CPU_NEXT(first_cpu)) {
+ kick_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, kick_tcg_thread,
&kick_timer);
+ timer_mod(kick_timer,
+ qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+ get_ticks_per_sec() / 10);
+ }
+
/* process any pending work */
atomic_mb_set(&exit_request, 1);
--
2.7.3
- [Qemu-devel] [RFC v1 05/11] target-arm/psci.c: wake up sleeping CPUs, (continued)
[Qemu-devel] [RFC v1 04/11] tcg: protect TBContext with tb_lock., Alex Bennée, 2016/03/18
[Qemu-devel] [RFC v1 08/11] tcg: add kick timer for single-threaded vCPU emulation,
Alex Bennée <=
[Qemu-devel] [RFC v1 07/11] tcg: add options for enabling MTTCG, Alex Bennée, 2016/03/18
[Qemu-devel] [RFC v1 10/11] tcg: grab iothread lock in cpu-exec interrupt handling, Alex Bennée, 2016/03/18
[Qemu-devel] [RFC v1 11/11] tcg: enable thread-per-vCPU, Alex Bennée, 2016/03/18
[Qemu-devel] [RFC v1 09/11] tcg: drop global lock during TCG code execution, Alex Bennée, 2016/03/18