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Date: Tue, 16 Dec 2008 13:10:53 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Eric Dumazet <dada1@...mosbay.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>,
Christoph Hellwig <hch@...radead.org>,
David Miller <davem@...emloft.net>,
"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
"kernel-testers@...r.kernel.org >> Kernel Testers List"
<kernel-testers@...r.kernel.org>, Mike Galbraith <efault@....de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Linux Netdev List <netdev@...r.kernel.org>,
Christoph Lameter <cl@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>
Subject: Re: [PATCH v3 2/7] fs: Use a percpu_counter to track nr_inodes
On Thu, Dec 11, 2008 at 11:39:10PM +0100, Eric Dumazet wrote:
> Avoids cache line ping pongs between cpus and prepare next patch,
> because updates of nr_inodes dont need inode_lock anymore.
>
> (socket8 bench result : no difference at this point)
I do like this per-CPU counter infrastructure!
One small comment change noted below. Other than that:
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
> ---
> fs/fs-writeback.c | 2 +-
> fs/inode.c | 39 +++++++++++++++++++++++++++++++--------
> include/linux/fs.h | 3 +++
> kernel/sysctl.c | 4 ++--
> mm/page-writeback.c | 2 +-
> 5 files changed, 38 insertions(+), 12 deletions(-)
>
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index d0ff0b8..b591cdd 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -608,7 +608,7 @@ void sync_inodes_sb(struct super_block *sb, int wait)
> unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
>
> wbc.nr_to_write = nr_dirty + nr_unstable +
> - (inodes_stat.nr_inodes - inodes_stat.nr_unused) +
> + (get_nr_inodes() - inodes_stat.nr_unused) +
> nr_dirty + nr_unstable;
> wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */
> sync_sb_inodes(sb, &wbc);
> diff --git a/fs/inode.c b/fs/inode.c
> index 0487ddb..f94f889 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -96,9 +96,33 @@ static DEFINE_MUTEX(iprune_mutex);
> * Statistics gathering..
> */
> struct inodes_stat_t inodes_stat;
> +static struct percpu_counter nr_inodes;
>
> static struct kmem_cache * inode_cachep __read_mostly;
>
> +int get_nr_inodes(void)
> +{
> + return percpu_counter_sum_positive(&nr_inodes);
> +}
> +
> +/*
> + * Handle nr_dentry sysctl
That would be "nr_inode", right?
> + */
> +#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
> +int proc_nr_inodes(ctl_table *table, int write, struct file *filp,
> + void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> + inodes_stat.nr_inodes = get_nr_inodes();
> + return proc_dointvec(table, write, filp, buffer, lenp, ppos);
> +}
> +#else
> +int proc_nr_inodes(ctl_table *table, int write, struct file *filp,
> + void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> + return -ENOSYS;
> +}
> +#endif
> +
> static void wake_up_inode(struct inode *inode)
> {
> /*
> @@ -306,9 +330,7 @@ static void dispose_list(struct list_head *head)
> destroy_inode(inode);
> nr_disposed++;
> }
> - spin_lock(&inode_lock);
> - inodes_stat.nr_inodes -= nr_disposed;
> - spin_unlock(&inode_lock);
> + percpu_counter_sub(&nr_inodes, nr_disposed);
> }
>
> /*
> @@ -560,8 +582,8 @@ struct inode *new_inode(struct super_block *sb)
>
> inode = alloc_inode(sb);
> if (inode) {
> + percpu_counter_inc(&nr_inodes);
> spin_lock(&inode_lock);
> - inodes_stat.nr_inodes++;
> list_add(&inode->i_list, &inode_in_use);
> list_add(&inode->i_sb_list, &sb->s_inodes);
> inode->i_ino = ++last_ino;
> @@ -622,7 +644,7 @@ static struct inode * get_new_inode(struct super_block *sb, struct hlist_head *h
> if (set(inode, data))
> goto set_failed;
>
> - inodes_stat.nr_inodes++;
> + percpu_counter_inc(&nr_inodes);
> list_add(&inode->i_list, &inode_in_use);
> list_add(&inode->i_sb_list, &sb->s_inodes);
> hlist_add_head(&inode->i_hash, head);
> @@ -671,7 +693,7 @@ static struct inode * get_new_inode_fast(struct super_block *sb, struct hlist_he
> old = find_inode_fast(sb, head, ino);
> if (!old) {
> inode->i_ino = ino;
> - inodes_stat.nr_inodes++;
> + percpu_counter_inc(&nr_inodes);
> list_add(&inode->i_list, &inode_in_use);
> list_add(&inode->i_sb_list, &sb->s_inodes);
> hlist_add_head(&inode->i_hash, head);
> @@ -1042,8 +1064,8 @@ void generic_delete_inode(struct inode *inode)
> list_del_init(&inode->i_list);
> list_del_init(&inode->i_sb_list);
> inode->i_state |= I_FREEING;
> - inodes_stat.nr_inodes--;
> spin_unlock(&inode_lock);
> + percpu_counter_dec(&nr_inodes);
>
> security_inode_delete(inode);
>
> @@ -1093,8 +1115,8 @@ static void generic_forget_inode(struct inode *inode)
> list_del_init(&inode->i_list);
> list_del_init(&inode->i_sb_list);
> inode->i_state |= I_FREEING;
> - inodes_stat.nr_inodes--;
> spin_unlock(&inode_lock);
> + percpu_counter_dec(&nr_inodes);
> if (inode->i_data.nrpages)
> truncate_inode_pages(&inode->i_data, 0);
> clear_inode(inode);
> @@ -1394,6 +1416,7 @@ void __init inode_init(void)
> {
> int loop;
>
> + percpu_counter_init(&nr_inodes, 0);
> /* inode slab cache */
> inode_cachep = kmem_cache_create("inode_cache",
> sizeof(struct inode),
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 114cb65..a789346 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -47,6 +47,7 @@ struct inodes_stat_t {
> int dummy[5]; /* padding for sysctl ABI compatibility */
> };
> extern struct inodes_stat_t inodes_stat;
> +extern int get_nr_inodes(void);
>
> extern int leases_enable, lease_break_time;
>
> @@ -2219,6 +2220,8 @@ int proc_nr_files(struct ctl_table *table, int write, struct file *filp,
> void __user *buffer, size_t *lenp, loff_t *ppos);
> int proc_nr_dentry(struct ctl_table *table, int write, struct file *filp,
> void __user *buffer, size_t *lenp, loff_t *ppos);
> +int proc_nr_inodes(struct ctl_table *table, int write, struct file *filp,
> + void __user *buffer, size_t *lenp, loff_t *ppos);
>
> int get_filesystem_list(char * buf);
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 777bee7..b705f3a 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1205,7 +1205,7 @@ static struct ctl_table fs_table[] = {
> .data = &inodes_stat,
> .maxlen = 2*sizeof(int),
> .mode = 0444,
> - .proc_handler = &proc_dointvec,
> + .proc_handler = &proc_nr_inodes,
> },
> {
> .ctl_name = FS_STATINODE,
> @@ -1213,7 +1213,7 @@ static struct ctl_table fs_table[] = {
> .data = &inodes_stat,
> .maxlen = 7*sizeof(int),
> .mode = 0444,
> - .proc_handler = &proc_dointvec,
> + .proc_handler = &proc_nr_inodes,
> },
> {
> .procname = "file-nr",
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 2970e35..a71a922 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -705,7 +705,7 @@ static void wb_kupdate(unsigned long arg)
> next_jif = start_jif + dirty_writeback_interval;
> nr_to_write = global_page_state(NR_FILE_DIRTY) +
> global_page_state(NR_UNSTABLE_NFS) +
> - (inodes_stat.nr_inodes - inodes_stat.nr_unused);
> + (get_nr_inodes() - inodes_stat.nr_unused);
> while (nr_to_write > 0) {
> wbc.more_io = 0;
> wbc.encountered_congestion = 0;
--
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