Re: [PATCH] sysinfo: include availram field in sysinfo struct

Cyrill Gorcunov
2022-01-06T16:11:43Z

On Thu, Jan 06, 2022 at 09:04:10PM +0530, Pintu Kumar wrote:
> 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.
>
> There are couple of places in kernel as well where this can be improved.
> For example:
> In fs/proc/meminfo.c:
> meminfo_proc_show:
> si_meminfo(&i);
> available = si_mem_available();
> Now with this change the second call be avoided.
> Thus, we can directly do:
> show_val_kb(m, "MemAvailable: ", i.availram);
>
> Note, this also requires update in procfs for free and other commands.
> Like in free command as well we frist call sysinfo then again parse
> /proc/meminfo to get available field.
> This can be avoided too with higher kernel version.
>
> A sample output with single sysinfo call is shown below:
> Total RAM: 248376 kB
> Free RAM: 231540 kB
> Avail RAM: 230448 kB
>
> Signed-off-by: Pintu Kumar <quic_pintu@quicinc.com>
> Signed-off-by: Pintu Agarwal <pintu.ping@gmail.com>
> ---
> include/uapi/linux/sysinfo.h | 1 +
> kernel/sys.c | 4 ++++
> mm/page_alloc.c | 2 ++
> 3 files changed, 7 insertions(+)
>
> diff --git a/include/uapi/linux/sysinfo.h b/include/uapi/linux/sysinfo.h
> index 435d5c2..6e77e90 100644
> --- a/include/uapi/linux/sysinfo.h
> +++ b/include/uapi/linux/sysinfo.h
> @@ -12,6 +12,7 @@ struct sysinfo {
> __kernel_ulong_t freeram; /* Available memory size */
> __kernel_ulong_t sharedram; /* Amount of shared memory */
> __kernel_ulong_t bufferram; /* Memory used by buffers */
> + __kernel_ulong_t availram; /* Memory available for allocation */
> __kernel_ulong_t totalswap; /* Total swap space size */
> __kernel_ulong_t freeswap; /* swap space still available */
> __u16 procs; /* Number of current processes */

Hi! Sorry, but I don't understand -- the sysinfo structure seems to
be part of user API, no? Don't we break it up here?