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>

1 files changed, 36 insertions, 0 deletions

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)