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

[pintu]

On 2021-03-03 01:48, Nitin Gupta wrote:
> > -----Original Message-----
> > From: pintu=codeaurora.org@xxxxxxxxxxxxxxxxx
> > <pintu=codeaurora.org@xxxxxxxxxxxxxxxxx> On Behalf Of Pintu Kumar
> > Sent: Tuesday, March 2, 2021 9:56 AM
> > To: linux-kernel@xxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; linux-
> > mm@xxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; pintu@xxxxxxxxxxxxxx;
> > iamjoonsoo.kim@xxxxxxx; sh_def@xxxxxxx; mateusznosek0@xxxxxxxxx;
> > bhe@xxxxxxxxxx; Nitin Gupta <nigupta@xxxxxxxxxx>; vbabka@xxxxxxx;
> > yzaikin@xxxxxxxxxx; keescook@xxxxxxxxxxxx; mcgrof@xxxxxxxxxx;
> > mgorman@xxxxxxxxxxxxxxxxxxx
> > Cc: pintu.ping@xxxxxxxxx
> > 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;

Thanks Nitin for your review.
You mean, you just wanted to retain this extern declaration ?
Any real benefit of keeping this declaration if not used elsewhere ?

> > No functionality is broken or changed this way.
> >
> > Signed-off-by: Pintu Kumar <pintu@xxxxxxxxxxxxxx>
> > Signed-off-by: Pintu Agarwal <pintu.ping@xxxxxxxxx>
> > ---
> >  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.

Sorry, I could not understand.
You mean to say just retain this last comment and only remove the 
variable ?
Again any real benefit you see in retaining this even if its not used?


Thanks,
Pintu