From: Patrick Donnelly <pdonnell@redhat.com>
Date: Thu, 6 Aug 2020 16:04:23 +0000 (-0700)
Subject: mds: add working set minimum for caps
X-Git-Tag: v17.0.0~1526^2~1
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=63392e1b65fbead6ef8c7acd6a70e6ef5b322390;p=ceph.git

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 457ad57c5c324..39d56304eac26 100644
--- 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 8869d6e1e21de..9953324d80c14 100644
--- 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 c57453fb70c54..4f190da4b5c32 100644
--- 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;