Skips setting the tb_lock if a process doesn't have more than one thread,
which is usually the case. Results in about 20% performance gain (measured
with the s390x target, but the effect should be similar with other targets).
Signed-off-by: Ulrich Hecht <u...@suse.de>
---
cpu-defs.h | 8 ++++++++
cpu-exec.c | 14 ++++++++++++--
linux-user/syscall.c | 1 +
3 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/cpu-defs.h b/cpu-defs.h
index 95068b5..c50c59e 100644
--- a/cpu-defs.h
+++ b/cpu-defs.h
@@ -135,6 +135,13 @@ typedef struct CPUWatchpoint {
} CPUWatchpoint;
#define CPU_TEMP_BUF_NLONGS 128
+
+#ifdef CONFIG_USER_ONLY
+#define MULTITHREAD uint32_t multithreaded;
+#else
+#define MULTITHREAD
+#endif
+
#define CPU_COMMON \
struct TranslationBlock *current_tb; /* currently executing TB */ \
/* soft mmu support */ \
@@ -149,6 +156,7 @@ typedef struct CPUWatchpoint {
uint32_t stop; /* Stop request */ \
uint32_t stopped; /* Artificially stopped */ \
uint32_t interrupt_request; \
+ MULTITHREAD /* needs locking when accessing TBs */ \
volatile sig_atomic_t exit_request; \
/* The meaning of the MMU modes is defined in the target code. */ \
CPUTLBEntry tlb_table[NB_MMU_MODES][CPU_TLB_SIZE]; \
diff --git a/cpu-exec.c b/cpu-exec.c
index 6b3391c..3fe2725 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -219,6 +219,9 @@ int cpu_exec(CPUState *env1)
TranslationBlock *tb;
uint8_t *tc_ptr;
unsigned long next_tb;
+#ifdef CONFIG_USER_ONLY
+ uint32_t multithreaded;
+#endif
if (cpu_halted(env1) == EXCP_HALTED)
return EXCP_HALTED;
@@ -576,7 +579,11 @@ int cpu_exec(CPUState *env1)
#endif
}
#endif
- spin_lock(&tb_lock);
+#ifdef CONFIG_USER_ONLY
+ multithreaded = env->multithreaded;
+ if (multithreaded)
+#endif
+ spin_lock(&tb_lock);
tb = tb_find_fast();
/* Note: we do it here to avoid a gcc bug on Mac OS X when
doing it in tb_find_slow */
@@ -600,7 +607,10 @@ int cpu_exec(CPUState *env1)
tb_add_jump((TranslationBlock *)(next_tb & ~3), next_tb &
3, tb);
}
}
- spin_unlock(&tb_lock);
+#ifdef CONFIG_USER_ONLY
+ if (multithreaded)
+#endif
+ spin_unlock(&tb_lock);
env->current_tb = tb;
/* cpu_interrupt might be called while translating the
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 617e031..f2a53d5 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3549,6 +3549,7 @@ static int do_fork(CPUState *env, unsigned int flags,
abi_ulong newsp,
ts = qemu_mallocz(sizeof(TaskState) + NEW_STACK_SIZE);
init_task_state(ts);
new_stack = ts->stack;
+ env->multithreaded = 1;
/* we create a new CPU instance. */
new_env = cpu_copy(env);
/* Init regs that differ from the parent. */
--
1.6.2.1
