linux-kernel - Re: [PATCH 18/45] writeback: introduce wait queue for balance_dirty

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Message-Id: <20091008145907.7f1799ca.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 8 Oct 2009 14:59:07 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>,
	Christoph Hellwig <hch@...radead.org>,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	Myklebust Trond <Trond.Myklebust@...app.com>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	Jan Kara <jack@...e.cz>, Nick Piggin <npiggin@...e.de>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 18/45] writeback: introduce wait queue for
 balance_dirty_pages()

On Thu, 8 Oct 2009 12:01:36 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> On Thu, Oct 08, 2009 at 10:40:37AM +0800, KAMEZAWA Hiroyuki wrote:
> > Thank you for clarification.
> > Then, hmm, %iotwait (which 'top' shows) didn't work as desgined and we need
> > to update throttle_vm_writeout() and some in vmscan.c. Thanks for input.
> 
> Thanks, you also reminds me to do io_schedule() in the nfs writeback
> wait queue :)
> 
good side effect ;)

> > BTW, I'm glad if I can know "how many threads/ios are throttoled now" per bdi.
> 
> Good suggestion. How about this patch?
> 

Seems attractive. 
Hmm..
==
struct dirty_throttle_task {
+	pid_t	owner_pid;
==
and show it ? (too verbose ?


Regards,
-Kame

> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  fs/fs-writeback.c           |    1 +
>  include/linux/backing-dev.h |    2 ++
>  mm/backing-dev.c            |   33 +++++++++++++++++++++++++++++++++
>  3 files changed, 36 insertions(+)
> 
> --- linux.orig/include/linux/backing-dev.h	2009-10-08 11:46:28.000000000 +0800
> +++ linux/include/linux/backing-dev.h	2009-10-08 11:47:39.000000000 +0800
> @@ -101,6 +101,7 @@ struct backing_dev_info {
>  #ifdef CONFIG_DEBUG_FS
>  	struct dentry *debug_dir;
>  	struct dentry *debug_stats;
> +	struct dentry *debug_throttle;
>  #endif
>  };
>  
> @@ -116,6 +117,7 @@ struct backing_dev_info {
>  #define DIRTY_THROTTLE_PAGES_STOP	(1 << 22)
>  
>  struct dirty_throttle_task {
> +	unsigned long		start_time;
>  	long			nr_pages;
>  	struct list_head	list;
>  	struct completion	complete;
> --- linux.orig/mm/backing-dev.c	2009-10-08 11:47:37.000000000 +0800
> +++ linux/mm/backing-dev.c	2009-10-08 11:59:06.000000000 +0800
> @@ -115,6 +115,23 @@ static int bdi_debug_stats_show(struct s
>  	return 0;
>  }
>  
> +static int bdi_debug_throttle_show(struct seq_file *m, void *v)
> +{
> +	struct backing_dev_info *bdi = m->private;
> +	struct dirty_throttle_task *tt;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&bdi->throttle_lock, flags);
> +	list_for_each_entry(tt, &bdi->throttle_list, list) {
> +		seq_printf(m, "goal=%lukb\twaited=%lums\n",
> +			   tt->nr_pages << (PAGE_SHIFT - 10),
> +			   (jiffies - tt->start_time) * 1000 / HZ);
> +	}
> +	spin_unlock_irqrestore(&bdi->throttle_lock, flags);
> +
> +	return 0;
> +}
> +
>  static int bdi_debug_stats_open(struct inode *inode, struct file *file)
>  {
>  	return single_open(file, bdi_debug_stats_show, inode->i_private);
> @@ -127,15 +144,31 @@ static const struct file_operations bdi_
>  	.release	= single_release,
>  };
>  
> +static int bdi_debug_throttle_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, bdi_debug_throttle_show, inode->i_private);
> +}
> +
> +static const struct file_operations bdi_debug_throttle_fops = {
> +	.open		= bdi_debug_throttle_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= single_release,
> +};
> +
>  static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
>  {
>  	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
>  	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
>  					       bdi, &bdi_debug_stats_fops);
> +	bdi->debug_throttle = debugfs_create_file("throttle_list", 0444,
> +						  bdi->debug_dir, bdi,
> +						  &bdi_debug_throttle_fops);
>  }
>  
>  static void bdi_debug_unregister(struct backing_dev_info *bdi)
>  {
> +	debugfs_remove(bdi->debug_throttle);
>  	debugfs_remove(bdi->debug_stats);
>  	debugfs_remove(bdi->debug_dir);
>  }
> --- linux.orig/fs/fs-writeback.c	2009-10-08 11:44:27.000000000 +0800
> +++ linux/fs/fs-writeback.c	2009-10-08 11:47:39.000000000 +0800
> @@ -284,6 +284,7 @@ static void bdi_calc_write_bandwidth(str
>  void bdi_writeback_wait(struct backing_dev_info *bdi, long nr_pages)
>  {
>  	struct dirty_throttle_task tt = {
> +		.start_time = jiffies,
>  		.nr_pages = nr_pages,
>  		.complete = COMPLETION_INITIALIZER_ONSTACK(tt.complete),
>  	};
> 

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