diff mbox series

[v3] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

Message ID Y5zT6B1mY9/pnwJV@tpad
State New
Headers
Series [v3] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs |

Commit Message

Marcelo Tosatti Dec. 16, 2022, 8:24 p.m. UTC 
  The coretemp driver uses rdmsr_on_cpu calls to read
MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
which contain information about current core temperature.

For certain low latency applications, the RDMSR interruption exceeds
the applications requirements.

So do not create core files in sysfs, for CPUs which have
isolation and nohz_full enabled.

Temperature information from the housekeeping cores should be
sufficient to infer die temperature.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
v3: do not create sysfs files for isolated CPUs (Guenter Roeck)
v2: improve changelog to mention that an error is returned,
     and sysfs file is not disabled (Guenter Roeck)

Comments

Guenter Roeck Dec. 28, 2022, 3:59 p.m. UTC | #1 
On Fri, Dec 16, 2022 at 05:24:08PM -0300, Marcelo Tosatti wrote:
> The coretemp driver uses rdmsr_on_cpu calls to read
> MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
> which contain information about current core temperature.
> 
> For certain low latency applications, the RDMSR interruption exceeds
> the applications requirements.
> 
> So do not create core files in sysfs, for CPUs which have
> isolation and nohz_full enabled.
> 
> Temperature information from the housekeeping cores should be
> sufficient to infer die temperature.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Applied to hwmon-next.

Thanks,
Guenter

> ---
> v3: do not create sysfs files for isolated CPUs (Guenter Roeck)
> v2: improve changelog to mention that an error is returned,
>      and sysfs file is not disabled (Guenter Roeck)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 9bee4d33fbdf..619dfde7a712 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -27,6 +27,7 @@
>  #include <asm/msr.h>
>  #include <asm/processor.h>
>  #include <asm/cpu_device_id.h>
> +#include <linux/sched/isolation.h>
>  
>  #define DRVNAME	"coretemp"
>  
> @@ -458,6 +459,9 @@ static int create_core_data(struct platform_device *pdev, unsigned int cpu,
>  	u32 eax, edx;
>  	int err, index, attr_no;
>  
> +	if (!housekeeping_cpu(cpu, HK_TYPE_MISC))
> +		return 0;
> +
>  	/*
>  	 * Find attr number for sysfs:
>  	 * We map the attr number to core id of the CPU
diff mbox series

Patch

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 9bee4d33fbdf..619dfde7a712 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -27,6 +27,7 @@ 
 #include <asm/msr.h>
 #include <asm/processor.h>
 #include <asm/cpu_device_id.h>
+#include <linux/sched/isolation.h>
 
 #define DRVNAME	"coretemp"
 
@@ -458,6 +459,9 @@  static int create_core_data(struct platform_device *pdev, unsigned int cpu,
 	u32 eax, edx;
 	int err, index, attr_no;
 
+	if (!housekeeping_cpu(cpu, HK_TYPE_MISC))
+		return 0;
+
 	/*
 	 * Find attr number for sysfs:
 	 * We map the attr number to core id of the CPU