RE: [PATCH] mm/compaction: remove unused variable sysctl_compact_memory

From: Nitin Gupta <nigupta@nvidia.com>
To: Pintu Kumar <pintu@codeaurora.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"iamjoonsoo.kim@lge.com" <iamjoonsoo.kim@lge.com>,
	"sh_def@163.com" <sh_def@163.com>,
	"mateusznosek0@gmail.com" <mateusznosek0@gmail.com>,
	"bhe@redhat.com" <bhe@redhat.com>,
	"vbabka@suse.cz" <vbabka@suse.cz>,
	"yzaikin@google.com" <yzaikin@google.com>,
	"keescook@chromium.org" <keescook@chromium.org>,
	"mcgrof@kernel.org" <mcgrof@kernel.org>,
	"mgorman@techsingularity.net" <mgorman@techsingularity.net>
Cc: "pintu.ping@gmail.com" <pintu.ping@gmail.com>
Subject: RE: [PATCH] mm/compaction: remove unused variable sysctl_compact_memory
Date: Tue, 2 Mar 2021 20:18:01 +0000	[thread overview]
Message-ID: <BYAPR12MB3416C9FD5D10AFB930E1C023D8999@BYAPR12MB3416.namprd12.prod.outlook.com> (raw)
In-Reply-To: <1614707773-10725-1-git-send-email-pintu@codeaurora.org>

> -----Original Message-----
> From: pintu=codeaurora.org@mg.codeaurora.org
> <pintu=codeaurora.org@mg.codeaurora.org> On Behalf Of Pintu Kumar
> Sent: Tuesday, March 2, 2021 9:56 AM
> To: linux-kernel@vger.kernel.org; akpm@linux-foundation.org; linux-
> mm@kvack.org; linux-fsdevel@vger.kernel.org; pintu@codeaurora.org;
> iamjoonsoo.kim@lge.com; sh_def@163.com; mateusznosek0@gmail.com;
> bhe@redhat.com; Nitin Gupta <nigupta@nvidia.com>; vbabka@suse.cz;
> yzaikin@google.com; keescook@chromium.org; mcgrof@kernel.org;
> mgorman@techsingularity.net
> Cc: pintu.ping@gmail.com
> Subject: [PATCH] mm/compaction: remove unused variable
> sysctl_compact_memory
> 
> External email: Use caution opening links or attachments
> 
> 
> The sysctl_compact_memory is mostly unsed in mm/compaction.c It just acts
> as a place holder for sysctl.
> 
> Thus we can remove it from here and move the declaration directly in
> kernel/sysctl.c itself.
> This will also eliminate the extern declaration from header file.

I prefer keeping the existing pattern of listing all compaction related tunables
together in compaction.h:

	extern int sysctl_compact_memory;
	extern unsigned int sysctl_compaction_proactiveness;
	extern int sysctl_extfrag_threshold;
	extern int sysctl_compact_unevictable_allowed;

> No functionality is broken or changed this way.
> 
> Signed-off-by: Pintu Kumar <pintu@codeaurora.org>
> Signed-off-by: Pintu Agarwal <pintu.ping@gmail.com>
> ---
>  include/linux/compaction.h | 1 -
>  kernel/sysctl.c            | 1 +
>  mm/compaction.c            | 3 ---
>  3 files changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h index
> ed4070e..4221888 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -81,7 +81,6 @@ static inline unsigned long compact_gap(unsigned int
> order)  }
> 
>  #ifdef CONFIG_COMPACTION
> -extern int sysctl_compact_memory;
>  extern unsigned int sysctl_compaction_proactiveness;  extern int
> sysctl_compaction_handler(struct ctl_table *table, int write,
>                         void *buffer, size_t *length, loff_t *ppos); diff --git
> a/kernel/sysctl.c b/kernel/sysctl.c index c9fbdd8..66aff21 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -198,6 +198,7 @@ static int max_sched_tunable_scaling =
> SCHED_TUNABLESCALING_END-1;  #ifdef CONFIG_COMPACTION  static int
> min_extfrag_threshold;  static int max_extfrag_threshold = 1000;
> +static int sysctl_compact_memory;
>  #endif
> 
>  #endif /* CONFIG_SYSCTL */
> diff --git a/mm/compaction.c b/mm/compaction.c index 190ccda..ede2886
> 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2650,9 +2650,6 @@ static void compact_nodes(void)
>                 compact_node(nid);
>  }
> 
> -/* The written value is actually unused, all memory is compacted */ -int
> sysctl_compact_memory;
> -

Please retain this comment for the tunable.

-Nitin