Re: [PATCH 1/3] nilfs2: remove nilfs_segctor_init() in segment.c

[Ryusuke Konishi <ryusuke-sG5X7nlA6pw@public.gmane.org>]

On Sun, 11 Apr 2010 12:17:26 +0800, Li Hong <lihong.hi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Sun, Apr 11, 2010 at 02:57:15AM +0900, Ryusuke Konishi wrote:
> > Hi,
> > On Sun, 11 Apr 2010 00:15:43 +0800, Li Hong <lihong.hi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > Hi KONISHI Ryusuke,
> > > 
> > > Three new patches based on nilfs2/for-next branch. New code has been built and
> > > loaded successfully, and also passed a light-weight reads and writes test.
> > > 
> > > Thanks,
> > > Li Hong
> > 
> > Ok, I'll look into each of them.
> > 
> > > ---------------------------- cut here --------------------------
> > > 
> > > From 2c622d0f59782321204bf1fde7eea4a593cc6b65 Mon Sep 17 00:00:00 2001
> > > From: Li Hong <lihong.hi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > > Date: Sat, 10 Apr 2010 21:57:11 +0800
> > > Subject: [PATCH 1/3] nilfs2: remove nilfs_segctor_init() in segment.c
> > > 
> > > There are only two lines of code in nilfs_segctor_init(). From a logic design
> > > view, the first line 'sci->sc_seq_done = sci->sc_seq_request;' should be put in
> > > nilfs_segctor_new(). Even in nilfs_segctor_new(), this initialization is
> > > needless because sci is kzalloc-ed. So nilfs_segctor_init() is only a wrap call
> > > to nilfs_segctor_start_thread(). This removes an indirect call overhead.
> > > 
> > > Signed-off-by: Li Hong <lihong.hi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > 
> > Looks no problem.
> > 
> > The reason why nilfs_segctor_init is present in that manner is
> > historical (just for your information. You don't have to mention this
> > reason).
> > 
> > I think you don't have to mention the indirect call overhead because
> > it's only triggered in the level of mount/unmount/remount and gcc will
> > inline it in the caller.
> ^^^^^^^^^^^^^^^^^^^^^^^^^
> No, there is no inline key word in nilfs_segctor_init().

> Unless you mean gcc will try to inline small procedures if possible.

I mean this ;)

By "objdump -D segment.o", you can actually see the function is
inlined in the caller.  It's a default thing nowadays unless
"noinline" keyword is specified.

Anyway, the only point I feel odd is the description.  Basically, I'd
like to apply this patch for cleanup.  May I remove the comment "this
removes an indrect call oveahead"?

Thanks,
Ryusuke Konishi

> Thanks,
> Li Hong
> 
> > Thanks,
> > Ryusuke Konishi
> > 
> > > ---
> > >  fs/nilfs2/segment.c |    9 +--------
> > >  1 files changed, 1 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
> > > index f235fc0..514620d 100644
> > > --- a/fs/nilfs2/segment.c
> > > +++ b/fs/nilfs2/segment.c
> > > @@ -2684,13 +2684,6 @@ static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
> > >  	}
> > >  }
> > >  
> > > -static int nilfs_segctor_init(struct nilfs_sc_info *sci)
> > > -{
> > > -	sci->sc_seq_done = sci->sc_seq_request;
> > > -
> > > -	return nilfs_segctor_start_thread(sci);
> > > -}
> > > -
> > >  /*
> > >   * Setup & clean-up functions
> > >   */
> > > @@ -2814,7 +2807,7 @@ int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
> > >  		return -ENOMEM;
> > >  
> > >  	nilfs_attach_writer(nilfs, sbi);
> > > -	err = nilfs_segctor_init(NILFS_SC(sbi));
> > > +	err = nilfs_segctor_start_thread(NILFS_SC(sbi));
> > >  	if (err) {
> > >  		nilfs_detach_writer(nilfs, sbi);
> > >  		kfree(sbi->s_sc_info);
> > > -- 
> > > 1.6.3.3
> > > 
> > > --
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