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Re: [Qemu-devel] [PATCH v2 3/3] target/arm: Rely on hflags correct in cp
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/3] target/arm: Rely on hflags correct in cpu_get_tb_cpu_state |
Date: |
Wed, 20 Feb 2019 10:33:07 +0000 |
User-agent: |
mu4e 1.1.0; emacs 26.1 |
Richard Henderson <address@hidden> writes:
> This is the payoff.
>
> From perf record -g data of ubuntu 18 boot and shutdown:
>
> BEFORE:
>
> - 23.02% 2.82% qemu-system-aar [.] helper_lookup_tb_ptr
> - 20.22% helper_lookup_tb_ptr
> + 10.05% tb_htable_lookup
> - 9.13% cpu_get_tb_cpu_state
> 3.20% aa64_va_parameters_both
> 0.55% fp_exception_el
>
> - 11.66% 4.74% qemu-system-aar [.] cpu_get_tb_cpu_state
> - 6.96% cpu_get_tb_cpu_state
> 3.63% aa64_va_parameters_both
> 0.60% fp_exception_el
> 0.53% sve_exception_el
>
> AFTER:
>
> - 16.40% 3.40% qemu-system-aar [.] helper_lookup_tb_ptr
> - 13.03% helper_lookup_tb_ptr
> + 11.19% tb_htable_lookup
> 0.55% cpu_get_tb_cpu_state
>
> 0.98% 0.71% qemu-system-aar [.] cpu_get_tb_cpu_state
>
> 0.87% 0.24% qemu-system-aar [.] rebuild_hflags_a64
>
> Before, helper_lookup_tb_ptr is the second hottest function in the
> application, consuming almost a quarter of the runtime. Within the
> entire execution, cpu_get_tb_cpu_state consumes about 12%.
>
> After, helper_lookup_tb_ptr has dropped to the fourth hottest function,
> with consumption dropping to a sixth of the runtime. Within the
> entire execution, cpu_get_tb_cpu_state has dropped below 1%, and the
> supporting function to rebuild hflags also consumes about 1%.
>
> Assertions are retained for --enable-debug-tcg.
>
> Signed-off-by: Richard Henderson <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
Tested-by: Alex Bennée <address@hidden>
> ---
> v2: Retain asserts for future debugging.
> ---
> target/arm/helper.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 909535a3e3..990a87876f 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -14034,19 +14034,29 @@ void HELPER(rebuild_hflags_a64)(CPUARMState *env,
> uint32_t el)
> void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
> target_ulong *cs_base, uint32_t *pflags)
> {
> - int current_el = arm_current_el(env);
> - uint32_t flags;
> + uint32_t flags = env->hflags;
> uint32_t pstate_for_ss;
>
> +#ifdef CONFIG_DEBUG_TCG
> + {
> + int el = arm_current_el(env);
> + uint32_t check_flags;
> + if (is_a64(env)) {
> + check_flags = rebuild_hflags_a64(env, el);
> + } else {
> + check_flags = rebuild_hflags_a32(env, el);
> + }
> + g_assert_cmphex(flags, ==, check_flags);
> + }
> +#endif
> +
> *cs_base = 0;
> - if (is_a64(env)) {
> + if (FIELD_EX32(flags, TBFLAG_ANY, AARCH64_STATE)) {
> *pc = env->pc;
> - flags = rebuild_hflags_a64(env, current_el);
> flags = FIELD_DP32(flags, TBFLAG_A64, BTYPE, env->btype);
> pstate_for_ss = env->pstate;
> } else {
> *pc = env->regs[15];
> - flags = rebuild_hflags_a32(env, current_el);
> flags = FIELD_DP32(flags, TBFLAG_A32, THUMB, env->thumb);
> flags = FIELD_DP32(flags, TBFLAG_A32, CONDEXEC, env->condexec_bits);
> pstate_for_ss = env->uncached_cpsr;
--
Alex Bennée
- [Qemu-devel] [PATCH v2 0/3] target/arm: Reduce overhead of cpu_get_tb_cpu_state, Richard Henderson, 2019/02/19
- [Qemu-devel] [PATCH v2 3/3] target/arm: Rely on hflags correct in cpu_get_tb_cpu_state, Richard Henderson, 2019/02/19
- Re: [Qemu-devel] [PATCH v2 3/3] target/arm: Rely on hflags correct in cpu_get_tb_cpu_state,
Alex Bennée <=
- [Qemu-devel] [PATCH v2 2/3] target/arm: Rebuild hflags at el changes and MSR writes, Richard Henderson, 2019/02/19
- [Qemu-devel] [PATCH v2 1/3] target/arm: Split out recompute_hflags et al, Richard Henderson, 2019/02/19
- Re: [Qemu-devel] [PATCH v2 0/3] target/arm: Reduce overhead of cpu_get_tb_cpu_state, no-reply, 2019/02/19
- Re: [Qemu-devel] [PATCH v2 0/3] target/arm: Reduce overhead of cpu_get_tb_cpu_state, no-reply, 2019/02/19
- Re: [Qemu-devel] [PATCH v2 0/3] target/arm: Reduce overhead of cpu_get_tb_cpu_state, Emilio G. Cota, 2019/02/21
- Re: [Qemu-devel] [PATCH v2 0/3] target/arm: Reduce overhead of cpu_get_tb_cpu_state, no-reply, 2019/02/27