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

David Laight
2022-01-07T22:22:27Z

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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