From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:44366 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728139AbeIMAeA (ORCPT ); Wed, 12 Sep 2018 20:34:00 -0400 Date: Wed, 12 Sep 2018 12:27:46 -0700 From: Liu Bo To: Nikolay Borisov Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: skip set_page_dirty if eb is dirty Message-ID: <20180912192745.elkmdpl5hyrawxks@US-160370MP2.local> Reply-To: bo.liu@linux.alibaba.com References: <1536703587-94565-1-git-send-email-bo.liu@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 > > 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 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); > >