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Date: Thu, 8 Oct 2009 15:39:45 +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 14:28:09 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:
> On Thu, Oct 08, 2009 at 01:59:07PM +0800, KAMEZAWA Hiroyuki wrote:
> > 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 ?
>
> Not all all, added comm too :)
>
Wow, nice.
Thank you,
-Kame
> ---
> writeback: show per-bdi throttled tasks
>
> All currently throttled tasks will be listed, showing the pages to
> writeback for them, and total wait time since blocked.
>
> # cat /debug/bdi/0:16/throttle_list
> goal=768kb waited=36ms pid=3551 comm=cp
>
>
> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
> fs/fs-writeback.c | 6 +++--
> include/linux/backing-dev.h | 3 ++
> mm/backing-dev.c | 35 ++++++++++++++++++++++++++++++++++
> 3 files changed, 42 insertions(+), 2 deletions(-)
>
> --- linux.orig/include/linux/backing-dev.h 2009-10-08 12:37:13.000000000 +0800
> +++ linux/include/linux/backing-dev.h 2009-10-08 14:10:44.000000000 +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 +117,8 @@ struct backing_dev_info {
> #define DIRTY_THROTTLE_PAGES_STOP (1 << 22)
>
> struct dirty_throttle_task {
> + struct task_struct *sleeper;
> + unsigned long start_time;
> long nr_pages;
> struct list_head list;
> struct completion complete;
> --- linux.orig/mm/backing-dev.c 2009-10-08 12:37:42.000000000 +0800
> +++ linux/mm/backing-dev.c 2009-10-08 14:12:35.000000000 +0800
> @@ -115,6 +115,25 @@ 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\tpid=%d\tcomm=%s\n",
> + tt->nr_pages << (PAGE_SHIFT - 10),
> + (jiffies - tt->start_time) * 1000 / HZ,
> + tt->sleeper->pid,
> + tt->sleeper->comm);
> + }
> + 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 +146,31 @@ 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 12:37:24.000000000 +0800
> +++ linux/fs/fs-writeback.c 2009-10-08 14:10:51.000000000 +0800
> @@ -284,8 +284,10 @@ static void bdi_calc_write_bandwidth(str
> void bdi_writeback_wait(struct backing_dev_info *bdi, long nr_pages)
> {
> struct dirty_throttle_task tt = {
> - .nr_pages = nr_pages,
> - .complete = COMPLETION_INITIALIZER_ONSTACK(tt.complete),
> + .sleeper = current,
> + .start_time = jiffies,
> + .nr_pages = nr_pages,
> + .complete = COMPLETION_INITIALIZER_ONSTACK(tt.complete),
> };
> unsigned long flags;
>
>
--
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