linux-kernel - Re: [f2fs-dev][PATCH]f2fs: avoid congestion_wait when do

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Date:	Mon, 07 Oct 2013 11:41:43 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	yuan zhong <yuan.mark.zhong@...sung.com>
Cc:	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	shu.tan@...sung.com
Subject: Re: [f2fs-dev][PATCH]f2fs: avoid congestion_wait when do_checkpoint
 for better performance

Hi,

Please do checkpatch.pl before sending a patch.
Thanks,

2013-09-30 (월), 18:28 +0800, yuan zhong:
> Previously,  do_checkpoint() will call congestion_wait() for waiting the pages (previous submitted node/meta/data pages) to be written back.
> Because congestion_wait() will set a regular period (e.g. HZ / 50 ) for waiting.
> For this reason, there is a situation that after the pages have been written back, but the checkpoint thread still wait for congestion_wait to exit.
> This is a problem here, especially, when sync a large number of small files or dirs.
> In order to avoid this, a wait_list is introduced, the checkpoint thread will be dropped into the wait_list if the pages have not been written back, and will be waked up by contrast.
> 
> Signed-off-by: Yuan Zhong <yuan.mark.zhong@...sung.com>
> ---
>  fs/f2fs/checkpoint.c |  3 +--
>  fs/f2fs/f2fs.h       | 19 +++++++++++++++++++
>  fs/f2fs/segment.c    |  1 +
>  fs/f2fs/super.c      |  1 +
>  4 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c index bb31220..cf6b4a5 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -756,8 +756,7 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, bool is_umount)
>  	f2fs_put_page(cp_page, 1);
>  
>  	/* wait for previous submitted node/meta pages writeback */
> -	while (get_pages(sbi, F2FS_WRITEBACK))
> -		congestion_wait(BLK_RW_ASYNC, HZ / 50);
> +	f2fs_writeback_wait(sbi);
>  
>  	filemap_fdatawait_range(sbi->node_inode->i_mapping, 0, LONG_MAX);
>  	filemap_fdatawait_range(sbi->meta_inode->i_mapping, 0, LONG_MAX); diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 608f0df..f8b62cc 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -18,6 +18,7 @@
>  #include <linux/crc32.h>
>  #include <linux/magic.h>
>  #include <linux/kobject.h>
> +#include <linux/wait.h>
>  
>  /*
>   * For mount options
> @@ -430,6 +431,8 @@ struct f2fs_sb_info {
>  	/* For sysfs suppport */
>  	struct kobject s_kobj;
>  	struct completion s_kobj_unregister;
> +	
> +	wait_queue_head_t writeback_wqh;
>  };
>  
>  /*
> @@ -961,6 +964,22 @@ static inline int f2fs_readonly(struct super_block *sb)
>  	return sb->s_flags & MS_RDONLY;
>  }
>  
> +static inline void f2fs_writeback_wait(struct f2fs_sb_info *sbi) {
> +	DEFINE_WAIT(wait);
> +
> +	prepare_to_wait(&sbi->writeback_wqh, &wait, TASK_UNINTERRUPTIBLE);
> +	if (get_pages(sbi, F2FS_WRITEBACK))
> +		io_schedule();
> +	finish_wait(&sbi->writeback_wqh, &wait); }
> +
> +static inline void f2fs_writeback_wake(struct f2fs_sb_info *sbi) {
> +	if (!get_pages(sbi, F2FS_WRITEBACK))
> +		wake_up_all(&sbi->writeback_wqh);
> +}
> +
>  /*
>   * file.c
>   */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 09af9c7..79293fe 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -597,6 +597,7 @@ static void f2fs_end_io_write(struct bio *bio, int err)
>  
>  	if (p->is_sync)
>  		complete(p->wait);
> +	f2fs_writeback_wake(p->sbi);	
>  	kfree(p);
>  	bio_put(bio);
>  }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 13d0a0f..b31f686 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -818,6 +818,7 @@ 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);
> +	init_waitqueue_head(&sbi->writeback_wqh);
>  	for (i = 0; i < NR_GLOBAL_LOCKS; i++)
>  		mutex_init(&sbi->fs_lock[i]);
>  	mutex_init(&sbi->node_write);
> 

-- 
Jaegeuk Kim
Samsung

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