diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2014-03-10 14:56:30 +0000 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2014-03-10 14:56:30 +0000 |
| commit | 72c1d3af6e9c2745edfeaa71918a68bcee4b79db (patch) | |
| tree | d7d01966c8d75f5427fc2a9bce5994b17fe79253 | |
| parent | 2b194951c592ad670ddf3bc5764216408ade46f8 (diff) | |
target-arm: Implement WFE as a yield operation
Implement WFE to yield our timeslice to the next CPU.
This avoids slowdowns in multicore configurations caused
by one core busy-waiting on a spinlock which can't possibly
be unlocked until the other core has an opportunity to run.
This speeds up my test case A15 dual-core boot by a factor
of three (though it is still four or five times slower than
a single-core boot).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1393339545-22111-1-git-send-email-peter.maydell@linaro.org
Reviewed-by: Richard Henderson <rth@twiddle.net>
Tested-by: Rob Herring <rob.herring@linaro.org>
| -rw-r--r-- | include/exec/cpu-defs.h | 1 | ||||
| -rw-r--r-- | target-arm/helper.h | 1 | ||||
| -rw-r--r-- | target-arm/op_helper.c | 9 | ||||
| -rw-r--r-- | target-arm/translate.c | 6 | ||||
| -rw-r--r-- | target-arm/translate.h | 2 |
5 files changed, 19 insertions, 0 deletions
diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h index 01cd8c7a2b..66a3d46938 100644 --- a/include/exec/cpu-defs.h +++ b/include/exec/cpu-defs.h @@ -59,6 +59,7 @@ typedef uint64_t target_ulong; #define EXCP_HLT 0x10001 /* hlt instruction reached */ #define EXCP_DEBUG 0x10002 /* cpu stopped after a breakpoint or singlestep */ #define EXCP_HALTED 0x10003 /* cpu is halted (waiting for external event) */ +#define EXCP_YIELD 0x10004 /* cpu wants to yield timeslice to another */ #define TB_JMP_CACHE_BITS 12 #define TB_JMP_CACHE_SIZE (1 << TB_JMP_CACHE_BITS) diff --git a/target-arm/helper.h b/target-arm/helper.h index 276f3a9149..8923f8ae71 100644 --- a/target-arm/helper.h +++ b/target-arm/helper.h @@ -50,6 +50,7 @@ DEF_HELPER_FLAGS_3(sel_flags, TCG_CALL_NO_RWG_SE, i32, i32, i32, i32) DEF_HELPER_2(exception, void, env, i32) DEF_HELPER_1(wfi, void, env) +DEF_HELPER_1(wfe, void, env) DEF_HELPER_3(cpsr_write, void, env, i32, i32) DEF_HELPER_1(cpsr_read, i32, env) diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c index 7d06d2f9a5..5851e041a0 100644 --- a/target-arm/op_helper.c +++ b/target-arm/op_helper.c @@ -225,6 +225,15 @@ void HELPER(wfi)(CPUARMState *env) cpu_loop_exit(env); } +void HELPER(wfe)(CPUARMState *env) +{ + /* Don't actually halt the CPU, just yield back to top + * level loop + */ + env->exception_index = EXCP_YIELD; + cpu_loop_exit(env); +} + void HELPER(exception)(CPUARMState *env, uint32_t excp) { env->exception_index = excp; diff --git a/target-arm/translate.c b/target-arm/translate.c index 253d2a13eb..df259debcc 100644 --- a/target-arm/translate.c +++ b/target-arm/translate.c @@ -3939,6 +3939,9 @@ static void gen_nop_hint(DisasContext *s, int val) s->is_jmp = DISAS_WFI; break; case 2: /* wfe */ + gen_set_pc_im(s, s->pc); + s->is_jmp = DISAS_WFE; + break; case 4: /* sev */ case 5: /* sevl */ /* TODO: Implement SEV, SEVL and WFE. May help SMP performance. */ @@ -10857,6 +10860,9 @@ static inline void gen_intermediate_code_internal(ARMCPU *cpu, case DISAS_WFI: gen_helper_wfi(cpu_env); break; + case DISAS_WFE: + gen_helper_wfe(cpu_env); + break; case DISAS_SWI: gen_exception(EXCP_SWI); break; diff --git a/target-arm/translate.h b/target-arm/translate.h index 67da6996c9..2f491f9ff6 100644 --- a/target-arm/translate.h +++ b/target-arm/translate.h @@ -44,6 +44,8 @@ extern TCGv_ptr cpu_env; * emitting unreachable code at the end of the TB in the A64 decoder */ #define DISAS_EXC 6 +/* WFE */ +#define DISAS_WFE 7 #ifdef TARGET_AARCH64 void a64_translate_init(void); |