RE: [PATCH v2] sysinfo: include availram field in sysinfo struct

[David Laight <David.Laight@ACULAB.COM>]

From: Pintu Kumar
> Sent: 07 January 2022 18:08
> 
> The sysinfo member does not have any "available ram" field and
> the bufferram field is not much helpful either, to get a rough
> estimate of available ram needed for allocation.
> 
> One needs to parse MemAvailable field separately from /proc/meminfo
> to get this info instead of directly getting if from sysinfo itself.
> 
> Thus, this patch introduce a new field as availram in sysinfo
> so that all the info total/free/available can be retrieved from
> one place itself.
> 
...
> diff --git a/include/uapi/linux/sysinfo.h b/include/uapi/linux/sysinfo.h
> index 435d5c2..fe84c6a 100644
> --- a/include/uapi/linux/sysinfo.h
> +++ b/include/uapi/linux/sysinfo.h
> @@ -19,7 +19,8 @@ struct sysinfo {
>  	__kernel_ulong_t totalhigh;	/* Total high memory size */
>  	__kernel_ulong_t freehigh;	/* Available high memory size */
>  	__u32 mem_unit;			/* Memory unit size in bytes */
> -	char _f[20-2*sizeof(__kernel_ulong_t)-sizeof(__u32)];	/* Padding: libc5 uses this.. */

There are 4 pad bytes here on most 64bit architectures.

> +	__kernel_ulong_t availram;	/* Memory available for allocation */
> +	char _f[20-3*sizeof(__kernel_ulong_t)-sizeof(__u32)];	/* Padding: libc5 uses this.. */
>  };

You've not compile-time tested the size of the structure.

	David

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