ceph: writeback congestion control

Set bdi congestion bit when amount of write data in flight exceeds adjustable
threshold.
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/addr.c

@@ -47,6 +47,12 @@
  * accounting is preserved.
  */
 
+#define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
+#define CONGESTION_OFF_THRESH(congestion_kb)				\
+	(CONGESTION_ON_THRESH(congestion_kb) -				\
+	 (CONGESTION_ON_THRESH(congestion_kb) >> 2))
+
+
 
 /*
  * Dirty a page.  Optimistically adjust accounting, on the assumption
@@ -377,6 +383,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 {
 	struct inode *inode;
 	struct ceph_inode_info *ci;
+	struct ceph_client *client;
 	struct ceph_osd_client *osdc;
 	loff_t page_off = page->index << PAGE_CACHE_SHIFT;
 	int len = PAGE_CACHE_SIZE;
@@ -384,6 +391,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	int err = 0;
 	struct ceph_snap_context *snapc;
 	u64 snap_size = 0;
+	long writeback_stat;
 
 	dout("writepage %p idx %lu\n", page, page->index);
 
@@ -393,7 +401,8 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	}
 	inode = page->mapping->host;
 	ci = ceph_inode(inode);
-	osdc = &ceph_inode_to_client(inode)->osdc;
+	client = ceph_inode_to_client(inode);
+	osdc = &client->osdc;
 
 	/* verify this is a writeable snap context */
 	snapc = (void *)page->private;
@@ -420,6 +429,11 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
 	dout("writepage %p page %p index %lu on %llu~%u\n",
 	     inode, page, page->index, page_off, len);
 
+	writeback_stat = atomic_long_inc_return(&client->writeback_count);
+	if (writeback_stat >
+	    CONGESTION_ON_THRESH(client->mount_args->congestion_kb))
+		set_bdi_congested(&client->backing_dev_info, BLK_RW_ASYNC);
+
 	set_page_writeback(page);
 	err = ceph_osdc_writepages(osdc, ceph_vino(inode),
 				   &ci->i_layout, snapc,
@@ -499,6 +513,8 @@ static void writepages_finish(struct ceph_osd_request *req,
 	struct writeback_control *wbc = req->r_wbc;
 	__s32 rc = -EIO;
 	u64 bytes = 0;
+	struct ceph_client *client = ceph_inode_to_client(inode);
+	long writeback_stat;
 
 	/* parse reply */
 	replyhead = msg->front.iov_base;
@@ -524,6 +540,13 @@ static void writepages_finish(struct ceph_osd_request *req,
 		BUG_ON(!page);
 		WARN_ON(!PageUptodate(page));
 
+		writeback_stat =
+			atomic_long_dec_return(&client->writeback_count);
+		if (writeback_stat <
+		    CONGESTION_OFF_THRESH(client->mount_args->congestion_kb))
+			clear_bdi_congested(&client->backing_dev_info,
+					    BLK_RW_ASYNC);
+
 		if (i >= wrote) {
 			dout("inode %p skipping page %p\n", inode, page);
 			wbc->pages_skipped++;
@@ -666,6 +689,7 @@ retry:
 		u64 offset, len;
 		struct ceph_osd_request_head *reqhead;
 		struct ceph_osd_op *op;
+		long writeback_stat;
 
 		next = 0;
 		locked_pages = 0;
@@ -773,6 +797,12 @@ get_more_pages:
 				first = i;
 			dout("%p will write page %p idx %lu\n",
 			     inode, page, page->index);
+
+			writeback_stat = atomic_long_inc_return(&client->writeback_count);
+			if (writeback_stat > CONGESTION_ON_THRESH(client->mount_args->congestion_kb)) {
+				set_bdi_congested(&client->backing_dev_info, BLK_RW_ASYNC);
+			}
+
 			set_page_writeback(page);
 			req->r_pages[locked_pages] = page;
 			locked_pages++;
@@ -998,7 +1028,8 @@ static int ceph_write_end(struct file *file, struct address_space *mapping,
 			  struct page *page, void *fsdata)
 {
 	struct inode *inode = file->f_dentry->d_inode;
-	struct ceph_mds_client *mdsc = &ceph_inode_to_client(inode)->mdsc;
+	struct ceph_client *client = ceph_inode_to_client(inode);
+	struct ceph_mds_client *mdsc = &client->mdsc;
 	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 	int check_cap = 0;
 

fs/ceph/debugfs.c

@@ -320,6 +320,30 @@ DEFINE_SHOW_FUNC(osdc_show)
 DEFINE_SHOW_FUNC(dentry_lru_show)
 DEFINE_SHOW_FUNC(caps_show)
 
+static int congestion_kb_set(void *data, u64 val)
+{
+	struct ceph_client *client = (struct ceph_client *)data;
+
+	if (client)
+		client->mount_args->congestion_kb = (int)val;
+
+	return 0;
+}
+
+static int congestion_kb_get(void *data, u64 *val)
+{
+	struct ceph_client *client = (struct ceph_client *)data;
+
+	if (client)
+		*val = (u64)client->mount_args->congestion_kb;
+
+	return 0;
+}
+
+
+DEFINE_SIMPLE_ATTRIBUTE(congestion_kb_fops, congestion_kb_get,
+			congestion_kb_set, "%llu\n");
+
 int __init ceph_debugfs_init(void)
 {
 	ceph_debugfs_dir = debugfs_create_dir("ceph", NULL);
@@ -409,6 +433,14 @@ int ceph_debugfs_client_init(struct ceph_client *client)
 	if (!client->debugfs_caps)
 		goto out;
 
+	client->debugfs_congestion_kb = debugfs_create_file("writeback_congestion_kb",
+						   0600,
+						   client->debugfs_dir,
+						   client,
+						   &congestion_kb_fops);
+	if (!client->debugfs_congestion_kb)
+		goto out;
+
 	sprintf(name, "../../bdi/%s", dev_name(client->sb->s_bdi->dev));
 	client->debugfs_bdi = debugfs_create_symlink("bdi", client->debugfs_dir,
 						     name);
@@ -431,6 +463,7 @@ void ceph_debugfs_client_cleanup(struct ceph_client *client)
 	debugfs_remove(client->osdc.debugfs_file);
 	debugfs_remove(client->mdsc.debugfs_file);
 	debugfs_remove(client->monc.debugfs_file);
+	debugfs_remove(client->debugfs_congestion_kb);
 	debugfs_remove(client->debugfs_dir);
 }
 

fs/ceph/super.c

@@ -150,6 +150,35 @@ static void ceph_inode_init_once(void *foo)
 	inode_init_once(&ci->vfs_inode);
 }
 
+static int default_congestion_kb(void)
+{
+	int congestion_kb;
+
+	/*
+	 * Copied from NFS
+	 *
+	 * congestion size, scale with available memory.
+	 *
+	 *  64MB:    8192k
+	 * 128MB:   11585k
+	 * 256MB:   16384k
+	 * 512MB:   23170k
+	 *   1GB:   32768k
+	 *   2GB:   46340k
+	 *   4GB:   65536k
+	 *   8GB:   92681k
+	 *  16GB:  131072k
+	 *
+	 * This allows larger machines to have larger/more transfers.
+	 * Limit the default to 256M
+	 */
+	congestion_kb = (16*int_sqrt(totalram_pages)) << (PAGE_SHIFT-10);
+	if (congestion_kb > 256*1024)
+		congestion_kb = 256*1024;
+
+	return congestion_kb;
+}
+
 static int __init init_caches(void)
 {
 	ceph_inode_cachep = kmem_cache_create("ceph_inode_info",
@@ -267,6 +296,7 @@ enum {
 	Opt_caps_wanted_delay_min,
 	Opt_caps_wanted_delay_max,
 	Opt_readdir_max_entries,
+	Opt_congestion_kb,
 	Opt_last_int,
 	/* int args above */
 	Opt_snapdirname,
@@ -295,6 +325,7 @@ static match_table_t arg_tokens = {
 	{Opt_caps_wanted_delay_min, "caps_wanted_delay_min=%d"},
 	{Opt_caps_wanted_delay_max, "caps_wanted_delay_max=%d"},
 	{Opt_readdir_max_entries, "readdir_max_entries=%d"},
+	{Opt_congestion_kb, "write_congestion_kb=%d"},
 	/* int args above */
 	{Opt_snapdirname, "snapdirname=%s"},
 	{Opt_name, "name=%s"},
@@ -342,6 +373,7 @@ static struct ceph_mount_args *parse_mount_args(int flags, char *options,
 	args->snapdir_name = kstrdup(CEPH_SNAPDIRNAME_DEFAULT, GFP_KERNEL);
 	args->cap_release_safety = CEPH_CAPS_PER_RELEASE * 4;
 	args->max_readdir = 1024;
+	args->congestion_kb = default_congestion_kb();
 
 	/* ip1[:port1][,ip2[:port2]...]:/subdir/in/fs */
 	err = -EINVAL;
@@ -445,6 +477,9 @@ static struct ceph_mount_args *parse_mount_args(int flags, char *options,
 		case Opt_readdir_max_entries:
 			args->max_readdir = intval;
 			break;
+		case Opt_congestion_kb:
+			args->congestion_kb = intval;
+			break;
 
 		case Opt_noshare:
 			args->flags |= CEPH_OPT_NOSHARE;
@@ -516,6 +551,7 @@ static struct ceph_client *ceph_create_client(struct ceph_mount_args *args)
 	client->msgr = NULL;
 
 	client->mount_err = 0;
+	atomic_long_set(&client->writeback_count, 0);
 
 	err = bdi_init(&client->backing_dev_info);
 	if (err < 0)

fs/ceph/super.h

@@ -59,6 +59,7 @@ struct ceph_mount_args {
 	int wsize;
 	int rsize;            /* max readahead */
 	int max_readdir;      /* max readdir size */
+	int congestion_kb;      /* max readdir size */
 	int osd_timeout;
 	char *snapdir_name;   /* default ".snap" */
 	char *name;
@@ -136,6 +137,7 @@ struct ceph_client {
 	struct workqueue_struct *wb_wq;
 	struct workqueue_struct *pg_inv_wq;
 	struct workqueue_struct *trunc_wq;
+	atomic_long_t writeback_count;
 
 	struct backing_dev_info backing_dev_info;
 
@@ -143,6 +145,7 @@ struct ceph_client {
 	struct dentry *debugfs_monmap;
 	struct dentry *debugfs_mdsmap, *debugfs_osdmap;
 	struct dentry *debugfs_dir, *debugfs_dentry_lru, *debugfs_caps;
+	struct dentry *debugfs_congestion_kb;
 	struct dentry *debugfs_bdi;
 #endif
 };