RE: [f2fs-dev] [PATCH 08/11] f2fs: fix wrong condition for unlikely

[Chao Yu]

Hi,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> Sent: Wednesday, July 30, 2014 11:18 AM
> To: Chao Yu
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [f2fs-dev] [PATCH 08/11] f2fs: fix wrong condition for unlikely
> 
> On Wed, Jul 30, 2014 at 09:44:43AM +0800, Chao Yu wrote:
> > Hi Jaegeuk,
> >
> > > -----Original Message-----
> > > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> > > Sent: Saturday, July 26, 2014 6:47 AM
> > > To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx;
> > > linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> > > Cc: Jaegeuk Kim
> > > Subject: [f2fs-dev] [PATCH 08/11] f2fs: fix wrong condition for unlikely
> > >
> > > This patch fixes the wrongly used unlikely condition.
> > >
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>

Reviewed-by: Chao Yu <chao2.yu@xxxxxxxxxxx>

> > > ---
> > >  fs/f2fs/checkpoint.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > > index 42a16c1..36b0d47 100644
> > > --- a/fs/f2fs/checkpoint.c
> > > +++ b/fs/f2fs/checkpoint.c
> > > @@ -932,7 +932,7 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, bool is_umount)
> > >  	/* Here, we only have one bio having CP pack */
> > >  	sync_meta_pages(sbi, META_FLUSH, LONG_MAX);
> > >
> > > -	if (unlikely(!is_set_ckpt_flags(ckpt, CP_ERROR_FLAG))) {
> > > +	if (!is_set_ckpt_flags(ckpt, CP_ERROR_FLAG)) {
> >
> > Maybe use likely(!is_set_ckpt_flags(ckpt, CP_ERROR_FLAG)) or
> >
> > if (unlikely(is_set_ckpt_flags(ckpt, CP_ERROR_FLAG)))
> > 	return;
> >
> > is more appropriate. How do you think?
> 
> Currently I'd like to put this without any likely or unlikely.
> Best thing is to measure some performance how this would make effect on.

I think we could get little improvement of performance if we use likely or unlikely
here. So if you'd like leave it without pre-judgment, it will be ok.
Let's just leave it as it was. :)

Thanks,

> Until then, it'd be better to do without it, since apparently this should
> not be unlikely.
> 
> How about you?
> Can we compare both of them explicitly?
> 
> Thanks,
> 
> >
> > >  		clear_prefree_segments(sbi);
> > >  		release_dirty_inode(sbi);
> > >  		F2FS_RESET_SB_DIRT(sbi);
> > > --
> > > 1.8.5.2 (Apple Git-48)
> > >
> > >
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