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Message-ID: <20180719111031.GX7193@dhcp22.suse.cz>
Date: Thu, 19 Jul 2018 13:10:31 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Kirill Tkhai <ktkhai@...tuozzo.com>
Cc: akpm@...ux-foundation.org, vdavydov.dev@...il.com,
penguin-kernel@...ove.SAKURA.ne.jp, chris@...is-wilson.co.uk,
gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: Keep int fields in struct shrink_control together
On Thu 19-07-18 13:51:19, Kirill Tkhai wrote:
> gfp_t is of unsigned type, so let's move nid to keep
> them together.
I guess you meant unsigned int so you can fill up a hole in
shrink_control and as such reduce the stack consumption a bit (at least
on 64b).
An output from pahole is usually a great tool to visualize this.
die__process_function: tag not supported (INVALID)!
struct shrink_control {
gfp_t gfp_mask; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
long unsigned int nr_to_scan; /* 8 8 */
long unsigned int nr_scanned; /* 16 8 */
int nid; /* 24 4 */
/* XXX 4 bytes hole, try to pack */
struct mem_cgroup * memcg; /* 32 8 */
/* size: 40, cachelines: 1, members: 5 */
/* sum members: 32, holes: 2, sum holes: 8 */
/* last cacheline: 40 bytes */
};
>
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
Acked-by: Michal Hocko <mhocko@...e.com>
> ---
> include/linux/shrinker.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index b154fd2b084c..d58aaaed34a4 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -12,6 +12,9 @@
> struct shrink_control {
> gfp_t gfp_mask;
>
> + /* current node being shrunk (for NUMA aware shrinkers) */
> + int nid;
> +
> /*
> * How many objects scan_objects should scan and try to reclaim.
> * This is reset before every call, so it is safe for callees
> @@ -26,9 +29,6 @@ struct shrink_control {
> */
> unsigned long nr_scanned;
>
> - /* current node being shrunk (for NUMA aware shrinkers) */
> - int nid;
> -
> /* current memcg being shrunk (for memcg aware shrinkers) */
> struct mem_cgroup *memcg;
> };
--
Michal Hocko
SUSE Labs
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