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[Qemu-devel] [RFC v4 14/28] tcg: add kick timer for single-threaded vCPU
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC v4 14/28] tcg: add kick timer for single-threaded vCPU emulation |
Date: |
Thu, 11 Aug 2016 16:24:10 +0100 |
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>
---
v2
- re-base fixes
- get_ticks_per_sec() -> NANOSECONDS_PER_SEC
v3
- add define for TCG_KICK_FREQ
- fix checkpatch warning
v4
- wrap next calc in inline qemu_tcg_next_kick() instead of macro
---
cpus.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/cpus.c b/cpus.c
index b5b45b8..8c49d6c 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1185,9 +1185,34 @@ static void deal_with_unplugged_cpus(void)
}
}
+/* 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 void qemu_cpu_kick_no_halt(void);
+
+#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
+
+static inline int64_t qemu_tcg_next_kick(void)
+{
+ return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
+}
+
+static void kick_tcg_thread(void *opaque)
+{
+ QEMUTimer *self = *(QEMUTimer **) opaque;
+ timer_mod(self, qemu_tcg_next_kick());
+ qemu_cpu_kick_no_halt();
+}
+
static void *qemu_tcg_cpu_thread_fn(void *arg)
{
CPUState *cpu = arg;
+ QEMUTimer *kick_timer;
rcu_register_thread();
@@ -1211,6 +1236,13 @@ 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_tcg_next_kick());
+ }
+
/* process any pending work */
atomic_mb_set(&exit_request, 1);
--
2.7.4
- [Qemu-devel] [RFC v4 01/28] cpus: make all_vcpus_paused() return bool, (continued)
- [Qemu-devel] [RFC v4 01/28] cpus: make all_vcpus_paused() return bool, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 03/28] translate-all: add DEBUG_LOCKING asserts, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 05/28] docs: new design document multi-thread-tcg.txt (DRAFTING), Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 08/28] translate-all: Add assert_(memory|tb)_lock annotations, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 10/28] target-arm/arm-powerctl: wake up sleeping CPUs, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 07/28] linux-user/elfload: ensure mmap_lock() held while setting up, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 06/28] tcg: comment on which functions have to be called with tb_lock held, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 15/28] tcg: rename tcg_current_cpu to tcg_current_rr_cpu, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 09/28] tcg: protect TBContext with tb_lock., Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 11/28] tcg: move tcg_exec_all and helpers above thread fn, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 14/28] tcg: add kick timer for single-threaded vCPU emulation,
Alex Bennée <=
- [Qemu-devel] [RFC v4 12/28] tcg: cpus rm tcg_exec_all(), Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 13/28] tcg: add options for enabling MTTCG, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 17/28] cpus: re-factor out handle_icount_deadline, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 18/28] tcg: remove global exit_request, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 19/28] tcg: move locking for tb_invalidate_phys_page_range up, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 16/28] tcg: drop global lock during TCG code execution, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 21/28] tcg: enable tb_lock() for SoftMMU, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 22/28] tcg: enable thread-per-vCPU, Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 25/28] cputlb: introduce tlb_flush_* async work., Alex Bennée, 2016/08/11
- [Qemu-devel] [RFC v4 23/28] atomic: introduce cmpxchg_bool, Alex Bennée, 2016/08/11