Re: [PATCH v3 1/1] monitor: Support specified vCPU registers

[Markus Armbruster]

zhenwei pi <pizhenwei@bytedance.com> writes:

> Originally we have to get all the vCPU registers and parse the
> specified one. To improve the performance of this usage, allow user
> specified vCPU id to query registers.
>
> Run a VM with 16 vCPU, use bcc tool to track the latency of
> 'hmp_info_registers':
> 'info registers -a' uses about 3ms;
> 'info registers 12' uses about 150us.
>
> Cc: Darren Kenny <darren.kenny@oracle.com>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  hmp-commands-info.hx |  8 +++++---
>  monitor/misc.c       | 10 ++++++++--
>  2 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index 188d9ece3b..dee072ac37 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -100,9 +100,11 @@ ERST
>  
>      {
>          .name       = "registers",
> -        .args_type  = "cpustate_all:-a",
> -        .params     = "[-a]",
> -        .help       = "show the cpu registers (-a: all - show register info 
> for all cpus)",
> +        .args_type  = "cpustate_all:-a,vcpu:i?",
> +        .params     = "[-a|vcpu]",
> +        .help       = "show the cpu registers (-a: all - show register info 
> for all cpus;"

Suggest to drop "all - ".

> +                      " vcpu: specific vCPU to query; show the current CPU's 
> registers if"
> +                      " no argument is specified)",
>          .cmd        = hmp_info_registers,
>      },
>  
> diff --git a/monitor/misc.c b/monitor/misc.c
> index 3d2312ba8d..74f7c4ea36 100644
> --- a/monitor/misc.c
> +++ b/monitor/misc.c
> @@ -307,6 +307,7 @@ int monitor_get_cpu_index(Monitor *mon)
>  static void hmp_info_registers(Monitor *mon, const QDict *qdict)
>  {
>      bool all_cpus = qdict_get_try_bool(qdict, "cpustate_all", false);
> +    int vcpu = qdict_get_try_int(qdict, "vcpu", -1);
>      CPUState *cs;
>  
>      if (all_cpus) {
> @@ -315,13 +316,18 @@ static void hmp_info_registers(Monitor *mon, const 
> QDict *qdict)
>              cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
>          }
>      } else {
> -        cs = mon_get_cpu(mon);
> +        cs = vcpu >= 0 ? qemu_get_cpu(vcpu) : mon_get_cpu(mon);
>  
>          if (!cs) {
> -            monitor_printf(mon, "No CPU available\n");
> +            if (vcpu >= 0) {
> +                monitor_printf(mon, "\nCPU#%d not available\n", vcpu);

Please drop the initial '\n'.

> +            } else {
> +                monitor_printf(mon, "No CPU available\n");
> +            }
>              return;
>          }
>  
> +        monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
>          cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
>      }
>  }

With the error message tweaked:
Reviewed-by: Markus Armbruster <armbru@redhat.com>