mds: add working set minimum for caps

A client may hold many inodes pinned in its cache for open files. That
client may be unable to release those caps to respond to cache pressure
from the MDS (or quiescent client cap recall). We should not complain if
that number of capabilities is reasonable (< 10k by default).

Fixes: https://tracker.ceph.com/issues/46830
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>

diff --git a/src/common/options.cc b/src/common/options.cc
index 457ad57c5c3245c394fda8f7320bd52a7481152e..39d56304eac26078ed9ae463d99b63ebcfd93cd8 100644 (file)
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -8320,6 +8320,11 @@ std::vector<Option> get_mds_options() {
     .set_default(100)
     .set_description("minimum number of capabilities a client may hold"),
 
+    Option("mds_min_caps_working_set", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+    .set_default(10000)
+    .set_flag(Option::FLAG_RUNTIME)
+    .set_description("number of capabilities a client may hold without cache pressure warnings generated"),
+
     Option("mds_max_caps_per_client", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
     .set_default(1_M)
     .set_description("maximum number of capabilities a client may hold"),

diff --git a/src/mds/Beacon.cc b/src/mds/Beacon.cc
index 8869d6e1e21de70b89cf7632c70abac4e371acb8..9953324d80c1433bb1541057119c6aed19dc077a 100644 (file)
--- a/src/mds/Beacon.cc
+++ b/src/mds/Beacon.cc
@@ -364,14 +364,16 @@ void Beacon::notify_health(MDSRank const *mds)
     set<Session*> sessions;
     mds->sessionmap.get_client_session_set(sessions);
 
+    const auto min_caps_working_set = g_conf().get_val<uint64_t>("mds_min_caps_working_set");
     const auto recall_warning_threshold = g_conf().get_val<Option::size_t>("mds_recall_warning_threshold");
     const auto max_completed_requests = g_conf()->mds_max_completed_requests;
     const auto max_completed_flushes = g_conf()->mds_max_completed_flushes;
     std::vector<MDSHealthMetric> late_recall_metrics;
     std::vector<MDSHealthMetric> large_completed_requests_metrics;
     for (auto& session : sessions) {
+      const uint64_t num_caps = session->get_num_caps();
       const uint64_t recall_caps = session->get_recall_caps();
-      if (recall_caps > recall_warning_threshold) {
+      if (recall_caps > recall_warning_threshold && num_caps > min_caps_working_set) {
         dout(2) << "Session " << *session <<
              " is not releasing caps fast enough. Recalled caps at " << recall_caps
           << " > " << recall_warning_threshold << " (mds_recall_warning_threshold)." << dendl;

diff --git a/src/mds/SessionMap.h b/src/mds/SessionMap.h
index c57453fb70c54a5e0d69bd3ca657dc84aa812124..4f190da4b5c32910e7f182a4aec5494f990600ea 100644 (file)
--- a/src/mds/SessionMap.h
+++ b/src/mds/SessionMap.h
@@ -354,6 +354,10 @@ public:
     return info.completed_flushes.count(tid);
   }
 
+  uint64_t get_num_caps() const {
+    return caps.size();
+  }
+
   unsigned get_num_completed_flushes() const { return info.completed_flushes.size(); }
   unsigned get_num_trim_flushes_warnings() const {
     return num_trim_flushes_warnings;