mds: add an option to decide whether prefetching entire dir or not.

Accessing one single dentry could be fastened by set this option to
false, when dir is not in the memory.
Signed-off-by: "Shen, Hang" <shenhang@kuaishou.com>

diff --git a/qa/cephfs/overrides/prefetch_entire_dirfrags/no.yaml b/qa/cephfs/overrides/prefetch_entire_dirfrags/no.yaml
new file mode 100644 (file)
index 0000000..41903ef
--- /dev/null
+++ b/qa/cephfs/overrides/prefetch_entire_dirfrags/no.yaml
@@ -0,0 +1,4 @@
+overrides:
+  ceph:
+    cephfs:
+      mds_dir_prefetch: false 

diff --git a/qa/cephfs/overrides/prefetch_entire_dirfrags/yes.yaml b/qa/cephfs/overrides/prefetch_entire_dirfrags/yes.yaml
new file mode 100644 (file)
index 0000000..143865a
--- /dev/null
+++ b/qa/cephfs/overrides/prefetch_entire_dirfrags/yes.yaml
@@ -0,0 +1,4 @@
+overrides:
+  ceph:
+    cephfs:
+      mds_dir_prefetch: true

diff --git a/qa/suites/fs/thrash/workloads/overrides/prefetch_entire_dirfrags b/qa/suites/fs/thrash/workloads/overrides/prefetch_entire_dirfrags
new file mode 120000 (symlink)
index 0000000..9b8024f
--- /dev/null
+++ b/qa/suites/fs/thrash/workloads/overrides/prefetch_entire_dirfrags
@@ -0,0 +1 @@
+.qa/cephfs/overrides/prefetch_entire_dirfrags
\ No newline at end of file

diff --git a/src/common/options/mds.yaml.in b/src/common/options/mds.yaml.in
index 697710484c8fc157205e5e1fec2fbe87c553ba1c..3a6464ebcdd71f9793fbdb188e6861902f50fd82 100644 (file)
--- a/src/common/options/mds.yaml.in
+++ b/src/common/options/mds.yaml.in
@@ -395,6 +395,15 @@ options:
   - mds
   flags:
   - runtime
+- name: mds_dir_prefetch
+  type: bool
+  level: advanced
+  desc: flag to prefetch entire dir
+  default: true
+  services:
+  - mds
+  flags:
+  - runtime
 - name: mds_tick_interval
   type: float
   level: advanced

diff --git a/src/mds/CDir.cc b/src/mds/CDir.cc
index 5bd44be7f4c14b89401f636577141ab5eac757c9..31b5eff331cbdf8edb3a304aec6416aed3af6c2a 100644 (file)
--- a/src/mds/CDir.cc
+++ b/src/mds/CDir.cc
@@ -1567,7 +1567,7 @@ void CDir::fetch(std::string_view dname, snapid_t last,
 
   // FIXME: to fetch a snap dentry, we need to get omap key in range
   //       [(name, last), (name, CEPH_NOSNAP))
-  if (!dname.empty() && last == CEPH_NOSNAP) {
+  if (!dname.empty() && last == CEPH_NOSNAP && !g_conf().get_val<bool>("mds_dir_prefetch")) {
     dentry_key_t key(last, dname, inode->hash_dentry_name(dname));
     fetch_keys({key}, c);
     return;
@@ -1594,7 +1594,7 @@ void CDir::fetch(std::string_view dname, snapid_t last,
 
 void CDir::fetch_keys(const std::vector<dentry_key_t>& keys, MDSContext *c)
 {
-  dout(10) << "fetch " << keys.size() << " keys on " << *this << dendl;
+  dout(10) << __func__ << " " << keys.size() << " keys on " << *this << dendl;
   ceph_assert(is_auth());
   ceph_assert(!is_complete());
 
@@ -2132,7 +2132,7 @@ void CDir::_omap_fetched(bufferlist& hdrbl, map<string, bufferlist>& omap,
   for (auto p = omap.rbegin(); p != omap.rend(); ++p, --pos) {
     string_snap_t key;
     dentry_key_t::decode_helper(p->first, key.name, key.snapid);
-    bool touch;
+    bool touch = false;
 
     if (key.snapid == CEPH_NOSNAP) {
       if (complete) {
@@ -2141,8 +2141,6 @@ void CDir::_omap_fetched(bufferlist& hdrbl, map<string, bufferlist>& omap,
        touch = proc_nulls_and_waiters(p->first, key);
       }
       last_name = std::string_view(p->first.c_str(), key.name.length());
-    } else {
-      touch = false;
     }
 
     CDentry *dn = nullptr;

diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index eb0bc7e645a0c83c98e912a197450f1e216e3a8c..8e97ee551990978e550964eb89dd3a35f45ce9a2 100644 (file)
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -5974,19 +5974,28 @@ bool MDCache::open_undef_inodes_dirfrags()
   map<CDir*, pair<bool, std::vector<dentry_key_t> > > fetch_queue;
   for (auto& dir : rejoin_undef_dirfrags) {
     ceph_assert(dir->get_version() == 0);
-    (void)fetch_queue[dir];
+    fetch_queue.emplace(std::piecewise_construct, std::make_tuple(dir), std::make_tuple());
   }
 
-  for (auto& in : rejoin_undef_inodes) {
-    assert(!in->is_base());
-    CDentry *dn = in->get_parent_dn();
-    auto& p = fetch_queue[dn->get_dir()];
-    if (dn->last != CEPH_NOSNAP) {
-      p.first = true;
-      p.second.clear();
-    } else if (!p.first) {
-      p.second.push_back(dn->key());
+  if (g_conf().get_val<bool>("mds_dir_prefetch")) {
+    for (auto& in : rejoin_undef_inodes) {
+      ceph_assert(!in->is_base());
+      ceph_assert(in->get_parent_dir());
+      fetch_queue.emplace(std::piecewise_construct, std::make_tuple(in->get_parent_dir()), std::make_tuple());
     }
+  } else {
+    for (auto& in : rejoin_undef_inodes) {
+      assert(!in->is_base());
+      CDentry *dn = in->get_parent_dn();
+      auto& p = fetch_queue[dn->get_dir()];
+
+      if (dn->last != CEPH_NOSNAP) {
+        p.first = true;
+        p.second.clear();
+      } else if (!p.first) {
+        p.second.push_back(dn->key());
+      }
+         }
   }
 
   if (fetch_queue.empty())