[PATCH] monitor: Support specified vCPU registers

[PATCH] monitor: Support specified vCPU registers

[zhenwei pi]

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 register 12' uses about 150us.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 hmp-commands-info.hx |  6 +++---
 monitor/misc.c       | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
index 3ffa24bd67..6023e2b5c5 100644
--- a/hmp-commands-info.hx
+++ b/hmp-commands-info.hx
@@ -100,9 +100,9 @@ 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; vcpu: vCPU to query)",
         .cmd        = hmp_info_registers,
     },
 
diff --git a/monitor/misc.c b/monitor/misc.c
index 3d2312ba8d..b12309faad 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) {
@@ -314,6 +315,24 @@ static void hmp_info_registers(Monitor *mon, const QDict *qdict)
             monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
             cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
         }
+    } else if (vcpu >= 0) {
+        CPUState *target_cs = NULL;
+
+        CPU_FOREACH(cs) {
+            if (cs->cpu_index == vcpu) {
+                target_cs = cs;
+                break;
+            }
+        }
+
+        if (!target_cs) {
+            monitor_printf(mon, "CPU#%d not available\n", vcpu);
+            return;
+        }
+
+        monitor_printf(mon, "\nCPU#%d\n", target_cs->cpu_index);
+        cpu_dump_state(target_cs, NULL, CPU_DUMP_FPU);
+        return;
     } else {
         cs = mon_get_cpu(mon);
 
-- 
2.20.1

PING: [PATCH] monitor: Support specified vCPU registers

[zhenwei pi]

PING!

On 7/19/22 15:55, zhenwei pi wrote:
> 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 register 12' uses about 150us.
> 
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>   hmp-commands-info.hx |  6 +++---
>   monitor/misc.c       | 19 +++++++++++++++++++
>   2 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index 3ffa24bd67..6023e2b5c5 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -100,9 +100,9 @@ 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; vcpu: vCPU to query)",
>           .cmd        = hmp_info_registers,
>       },
>   
> diff --git a/monitor/misc.c b/monitor/misc.c
> index 3d2312ba8d..b12309faad 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) {
> @@ -314,6 +315,24 @@ static void hmp_info_registers(Monitor *mon, const QDict *qdict)
>               monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
>               cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
>           }
> +    } else if (vcpu >= 0) {
> +        CPUState *target_cs = NULL;
> +
> +        CPU_FOREACH(cs) {
> +            if (cs->cpu_index == vcpu) {
> +                target_cs = cs;
> +                break;
> +            }
> +        }
> +
> +        if (!target_cs) {
> +            monitor_printf(mon, "CPU#%d not available\n", vcpu);
> +            return;
> +        }
> +
> +        monitor_printf(mon, "\nCPU#%d\n", target_cs->cpu_index);
> +        cpu_dump_state(target_cs, NULL, CPU_DUMP_FPU);
> +        return;
>       } else {
>           cs = mon_get_cpu(mon);
>   

-- 
zhenwei pi

Re: [PATCH] monitor: Support specified vCPU registers

[Darren Kenny]

On Tuesday, 2022-07-19 at 15:55:44 +08, zhenwei pi wrote:
> 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 register 12' uses about 150us.

TYPO: I'm assuming that should be 'info registers 12'?

>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  hmp-commands-info.hx |  6 +++---
>  monitor/misc.c       | 19 +++++++++++++++++++
>  2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
> index 3ffa24bd67..6023e2b5c5 100644
> --- a/hmp-commands-info.hx
> +++ b/hmp-commands-info.hx
> @@ -100,9 +100,9 @@ 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]",

From what I can see in the code, only one of these may be specified at a
time - or at least, '-a' will take precedence.

Maybe it would read more correctly as '[-a|vcpu]' ?

> +        .help       = "show the cpu registers (-a: all - show register info for all cpus; vcpu: vCPU to query)",

Possibly also it would be worth saying "...; vcpu: specific vCPU to query"?

>          .cmd        = hmp_info_registers,
>      },
>  
> diff --git a/monitor/misc.c b/monitor/misc.c
> index 3d2312ba8d..b12309faad 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) {
> @@ -314,6 +315,24 @@ static void hmp_info_registers(Monitor *mon, const QDict *qdict)
>              monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
>              cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
>          }
> +    } else if (vcpu >= 0) {
> +        CPUState *target_cs = NULL;
> +
> +        CPU_FOREACH(cs) {
> +            if (cs->cpu_index == vcpu) {
> +                target_cs = cs;
> +                break;
> +            }
> +        }
> +
> +        if (!target_cs) {
> +            monitor_printf(mon, "CPU#%d not available\n", vcpu);
> +            return;
> +        }
> +
> +        monitor_printf(mon, "\nCPU#%d\n", target_cs->cpu_index);
> +        cpu_dump_state(target_cs, NULL, CPU_DUMP_FPU);
> +        return;

This return call seems unnecessary here.

Thanks,

Darren.