On Wed, Sep 12, 2018 at 09:37:20AM +0300, Nikolay Borisov wrote:
>
>
> On 12.09.2018 01:06, Liu Bo wrote:
> > As long as @eb is marked with EXTENT_BUFFER_DIRTY, all of its pages
> > are dirty, so no need to set pages dirty again.
> >
> > Signed-off-by: Liu Bo <bo.liu@xxxxxxxxxxxxxxxxx>
>
> Does make it any performance difference, numbers?
>
To be honest, the performance difference would be trivial in a normal
big test round. But I just looked into the difference from my ftrace,
removing the loop can reduce the time spent by 10us in my box.
> Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Thanks a lot for reviewing.
thanks,
-liubo
> > ---
> > fs/btrfs/extent_io.c | 11 +++++++----
> > fs/btrfs/extent_io.h | 2 +-
> > 2 files changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index 628f1aef34b0..fb2bf50134a1 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -5165,11 +5165,11 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
> > WARN_ON(atomic_read(&eb->refs) == 0);
> > }
> >
> > -int set_extent_buffer_dirty(struct extent_buffer *eb)
> > +bool set_extent_buffer_dirty(struct extent_buffer *eb)
> > {
> > int i;
> > int num_pages;
> > - int was_dirty = 0;
> > + bool was_dirty;
> >
> > check_buffer_tree_ref(eb);
> >
> > @@ -5179,8 +5179,11 @@ int set_extent_buffer_dirty(struct extent_buffer *eb)
> > WARN_ON(atomic_read(&eb->refs) == 0);
> > WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
> >
> > - for (i = 0; i < num_pages; i++)
> > - set_page_dirty(eb->pages[i]);
> > + if (!was_dirty) {
> > + for (i = 0; i < num_pages; i++)
> > + set_page_dirty(eb->pages[i]);
> > + }
> > +
> > return was_dirty;
> > }
> >
> > diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> > index b4d03e677e1d..f2ab42d57f02 100644
> > --- a/fs/btrfs/extent_io.h
> > +++ b/fs/btrfs/extent_io.h
> > @@ -479,7 +479,7 @@ void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
> > void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
> > unsigned long pos, unsigned long len);
> > void clear_extent_buffer_dirty(struct extent_buffer *eb);
> > -int set_extent_buffer_dirty(struct extent_buffer *eb);
> > +bool set_extent_buffer_dirty(struct extent_buffer *eb);
> > void set_extent_buffer_uptodate(struct extent_buffer *eb);
> > void clear_extent_buffer_uptodate(struct extent_buffer *eb);
> > int extent_buffer_under_io(struct extent_buffer *eb);
> >
