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.
Another question is what is ->writepages in sbi used for? I'm not quite clear.
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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