Hi Chao,
On Wed, Jul 30, 2014 at 09:07:49PM +0800, Chao Yu wrote:
> Hi Jaegeuk Changman,
>
> > -----Original Message-----
> > From: Chao Yu [mailto:chao2...@samsung.com]
> > Sent: Thursday, July 03, 2014 6:59 PM
> > To: Jaegeuk Kim; Changman Lee
> > Cc: linux-fsde...@vger.kernel.org; linux-kernel@vger.kernel.org;
> > linux-f2fs-de...@lists.sourceforge.net
> > Subject: [f2fs-dev] [PATCH] f2fs: reduce competition among node page writes
> >
> > We do not need to block on ->node_write among different node page writers
> > e.g.
> > fsync/flush, unless we have a node page writer from write_checkpoint.
> > So it's better use rw_semaphore instead of mutex type for ->node_write to
> > promote performance.
>
> If you could have time to help explaining the problem of this patch, I will be
> appreciated for that.
I have no clue. Except checkpoint, I don't know why need to block to
write node page.
Do you have any problem when you test with this patch?
>
> Another question is what is ->writepages in sbi used for? I'm not quite clear.
>
I remember it is for writing data pages per thread as much as possible.
When multi-threads write some files simultaneously, multi-threads contended with
each other to allocate a block. So block allocation was interleaved
across threads. It makes fragmentation of file.
Thanks,
> Thanks,
>
> >
> > Signed-off-by: Chao Yu <chao2...@samsung.com>
> > ---
> > fs/f2fs/checkpoint.c | 6 +++---
> > fs/f2fs/f2fs.h | 2 +-
> > fs/f2fs/node.c | 4 ++--
> > fs/f2fs/super.c | 2 +-
> > 4 files changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > index 0b4710c..eec406b 100644
> > --- a/fs/f2fs/checkpoint.c
> > +++ b/fs/f2fs/checkpoint.c
> > @@ -714,10 +714,10 @@ retry_flush_dents:
> > * until finishing nat/sit flush.
> > */
> > retry_flush_nodes:
> > - mutex_lock(&sbi->node_write);
> > + down_write(&sbi->node_write);
> >
> > if (get_pages(sbi, F2FS_DIRTY_NODES)) {
> > - mutex_unlock(&sbi->node_write);
> > + up_write(&sbi->node_write);
> > sync_node_pages(sbi, 0, &wbc);
> > goto retry_flush_nodes;
> > }
> > @@ -726,7 +726,7 @@ retry_flush_nodes:
> >
> > static void unblock_operations(struct f2fs_sb_info *sbi)
> > {
> > - mutex_unlock(&sbi->node_write);
> > + up_write(&sbi->node_write);
> > f2fs_unlock_all(sbi);
> > }
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index ae3b4ac..ca30b5a 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -444,7 +444,7 @@ struct f2fs_sb_info {
> > struct inode *meta_inode; /* cache meta blocks */
> > struct mutex cp_mutex; /* checkpoint procedure lock */
> > struct rw_semaphore cp_rwsem; /* blocking FS operations */
> > - struct mutex node_write; /* locking node writes */
> > + struct rw_semaphore node_write; /* locking node writes */
> > struct mutex writepages; /* mutex for writepages() */
> > bool por_doing; /* recovery is doing or not */
> > wait_queue_head_t cp_wait;
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index a90f51d..7b5b5de 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -1231,12 +1231,12 @@ static int f2fs_write_node_page(struct page *page,
> > if (wbc->for_reclaim)
> > goto redirty_out;
> >
> > - mutex_lock(&sbi->node_write);
> > + down_read(&sbi->node_write);
> > set_page_writeback(page);
> > write_node_page(sbi, page, &fio, nid, ni.blk_addr, &new_addr);
> > set_node_addr(sbi, &ni, new_addr, is_fsync_dnode(page));
> > dec_page_count(sbi, F2FS_DIRTY_NODES);
> > - mutex_unlock(&sbi->node_write);
> > + up_read(&sbi->node_write);
> > unlock_page(page);
> > return 0;
> >
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 8f96d93..bed9413 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -947,7 +947,7 @@ static int f2fs_fill_super(struct super_block *sb, void
> > *data, int silent)
> > mutex_init(&sbi->gc_mutex);
> > mutex_init(&sbi->writepages);
> > mutex_init(&sbi->cp_mutex);
> > - mutex_init(&sbi->node_write);
> > + init_rwsem(&sbi->node_write);
> > sbi->por_doing = false;
> > spin_lock_init(&sbi->stat_lock);
> >
> > --
> > 1.7.9.5
> >
> >
> >
> > ------------------------------------------------------------------------------
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