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Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP |
Date: |
Mon, 7 Sep 2020 18:49:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 9/7/20 6:30 PM, Claudio Fontana wrote:
> On 9/7/20 12:20 PM, Philippe Mathieu-Daudé wrote:
>> On 9/7/20 12:05 PM, Claudio Fontana wrote:
>>> Hi Richard,
>>>
>>> currently rebasing on top of this one,
>>> just a question, why is the patch not directly using "current_machine"?
>>
>> For user mode?
>
> In user mode I'd not expect softmmu/cpus.c to be built at all...
Which is why :) current_machine is NULL in user-mode.
>
> Ciao,
>
> Claudio
>
>>
>>>
>>> Is using MACHINE(qdev_get_machine()) preferrable here?
>>>
>>> Thanks,
>>>
>>> Claudio
>>>
>>> On 9/3/20 11:40 PM, Richard Henderson wrote:
>>>> Do not set parallel_cpus if there is only one cpu instantiated.
>>>> This will allow tcg to use serial code to implement atomics.
>>>>
>>>> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>>> ---
>>>> softmmu/cpus.c | 11 ++++++++++-
>>>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/softmmu/cpus.c b/softmmu/cpus.c
>>>> index a802e899ab..e3b98065c9 100644
>>>> --- a/softmmu/cpus.c
>>>> +++ b/softmmu/cpus.c
>>>> @@ -1895,6 +1895,16 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
>>>> if (!tcg_region_inited) {
>>>> tcg_region_inited = 1;
>>>> tcg_region_init();
>>>> + /*
>>>> + * If MTTCG, and we will create multiple cpus,
>>>> + * then we will have cpus running in parallel.
>>>> + */
>>>> + if (qemu_tcg_mttcg_enabled()) {
>>>> + MachineState *ms = MACHINE(qdev_get_machine());
>>>
>>> MachineState *ms = current_machine;
>>> ?
>>>
>>>
>>>> + if (ms->smp.max_cpus > 1) {
>>>> + parallel_cpus = true;
>>>> + }
>>>> + }
>>>> }
>>>>
>>>> if (qemu_tcg_mttcg_enabled() || !single_tcg_cpu_thread) {
>>>> @@ -1904,7 +1914,6 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
>>>>
>>>> if (qemu_tcg_mttcg_enabled()) {
>>>> /* create a thread per vCPU with TCG (MTTCG) */
>>>> - parallel_cpus = true;
>>>> snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
>>>> cpu->cpu_index);
>>>>
>>>>
>>>
>>>
>
>
- [PULL 0/5] tcg patch queue, Richard Henderson, 2020/09/03
- [PULL 1/5] cputlb: Make store_helper less fragile to compiler optimizations, Richard Henderson, 2020/09/03
- [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Richard Henderson, 2020/09/03
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Claudio Fontana, 2020/09/07
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Philippe Mathieu-Daudé, 2020/09/07
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Claudio Fontana, 2020/09/07
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP,
Philippe Mathieu-Daudé <=
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Claudio Fontana, 2020/09/08
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Philippe Mathieu-Daudé, 2020/09/08
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Claudio Fontana, 2020/09/10
- Re: [PULL 3/5] softmmu/cpus: Only set parallel_cpus for SMP, Philippe Mathieu-Daudé, 2020/09/10
[PULL 2/5] tcg: Fix tcg gen for vectorized absolute value, Richard Henderson, 2020/09/03
[PULL 4/5] tcg: Eliminate one store for in-place 128-bit dup_mem, Richard Henderson, 2020/09/03
[PULL 5/5] tcg: Implement 256-bit dup for tcg_gen_gvec_dup_mem, Richard Henderson, 2020/09/03
Re: [PULL 0/5] tcg patch queue, Peter Maydell, 2020/09/06