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>
(cherry picked from commit 63392e1b65fbead6ef8c7acd6a70e6ef5b322390)

diff --git a/src/common/options.cc b/src/common/options.cc
index f76a623149472867515b343e10ce1c47aec74d50..b45bcd2f35e3088800fb9700af25e46f9140e007 100644 (file)
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -8188,6 +8188,11 @@ 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 c6da7cd242a596e5e8347af474470e38440af0ce..fccac994b77e3c48b8fbc1ce0dea8f597b456e1a 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 9fec9ded997ae33edb719074fdfc39979d031dc2..1d2555c4c8a35cc521dc94fbd5d9d858ead79667 100644 (file)
--- a/src/mds/SessionMap.h
+++ b/src/mds/SessionMap.h
@@ -358,6 +358,10 @@ 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;