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>

4 files changed, 105 insertions, 2 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index d0cdceb0b90b..a6850a14038e 100644
--- a/fs/ceph/addr.c
+++ b/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;
 
diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
index 441484ab7e94..22d3b47fb1be 100644
--- a/fs/ceph/debugfs.c
+++ b/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);
 }
 
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 6d02a166f8ff..b9cb8cebcdc1 100644
--- a/fs/ceph/super.c
+++ b/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)
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 2304bd2844a4..62d9ae482d72 100644
--- a/fs/ceph/super.h
+++ b/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
 };