From 2e1141e43980a0a44b18159860ebf9cc38316435 Mon Sep 17 00:00:00 2001
From: Aishwarya Mathuria <amathuri@redhat.com>
Date: Fri, 12 Mar 2021 16:57:40 +0530
Subject: [PATCH] mon: Modifying trim logic to change paxos_service_trim_max
 dynamically

 Currently, the Paxos Service trim logic is bounded by a max value (paxos_service_trim_max). This change dynamically modifies the max value when the number of logs to be trimmed is higher than paxos_service_trim_max.

 The paxos_service_trim_max_multiplier has been added in case we want to increase paxos_service_trim_max by a certain factor. If this option is enabled we get a new upper bound when trim sizes are high.

Fixes: https://tracker.ceph.com/issues/50004

Signed-off-by: Aishwarya Mathuria <amathuri@redhat.com>
---
 doc/rados/configuration/mon-config-ref.rst | 10 +++++++-
 src/common/options.cc                      | 11 ++++++--
 src/mon/PaxosService.cc                    | 29 +++++++++++++++-------
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/doc/rados/configuration/mon-config-ref.rst b/doc/rados/configuration/mon-config-ref.rst
index fbf50b53de99..02e9b6b79dc6 100644
--- a/doc/rados/configuration/mon-config-ref.rst
+++ b/doc/rados/configuration/mon-config-ref.rst
@@ -766,7 +766,15 @@ Trimming requires that the placement groups are ``active+clean``.
 :Default: ``500``
 
 
-``mon_mds_force_trim_to``
+``paxos service trim max multiplier``
+
+:Description: The factor by which paxos service trim max will be multiplied
+              to get a new upper bound when trim sizes are high (0 disables it)
+:Type: Integer
+:Default: ``20``
+
+
+``mon mds force trim to``
 
 :Description: Force monitor to trim mdsmaps to this point (0 disables it.
               dangerous, use with care)
diff --git a/src/common/options.cc b/src/common/options.cc
index 8003b4bdcb60..c325e03d69fb 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -2281,16 +2281,23 @@ std::vector<Option> get_global_options() {
     .add_service("mon")
     .set_description(""),
 
-    Option("paxos_service_trim_min", Option::TYPE_INT, Option::LEVEL_ADVANCED)
+    Option("paxos_service_trim_min", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
     .set_default(250)
     .add_service("mon")
     .set_description(""),
 
-    Option("paxos_service_trim_max", Option::TYPE_INT, Option::LEVEL_ADVANCED)
+    Option("paxos_service_trim_max", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
     .set_default(500)
     .add_service("mon")
     .set_description(""),
 
+    Option("paxos_service_trim_max_multiplier", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+    .set_default(20)
+    .set_min(0)
+    .add_service("mon")
+    .set_description("factor by which paxos_service_trim_max will be multiplied to get a new upper bound when trim sizes are high  (0 disables it)")
+    .set_flag(Option::FLAG_RUNTIME),
+
     Option("paxos_kill_at", Option::TYPE_INT, Option::LEVEL_DEV)
     .set_default(0)
     .add_service("mon")
diff --git a/src/mon/PaxosService.cc b/src/mon/PaxosService.cc
index 8366bc704b57..94caea425747 100644
--- a/src/mon/PaxosService.cc
+++ b/src/mon/PaxosService.cc
@@ -393,15 +393,26 @@ void PaxosService::maybe_trim()
     return;
   }
 
-  const version_t trim_max = g_conf().get_val<version_t>("paxos_service_trim_max");
-  if (trim_max > 0 &&
-      to_remove > trim_max) {
-    dout(10) << __func__ << " trim_to " << trim_to << " would only trim " << to_remove
-	     << " > paxos_service_trim_max, limiting to " << trim_max
-	     << dendl;
-    trim_to = get_first_committed() + trim_max;
-    to_remove = trim_max;
-  }
+  to_remove = [to_remove, this] {
+    const version_t trim_max = g_conf().get_val<version_t>("paxos_service_trim_max");
+    if (trim_max == 0 || to_remove < trim_max) {
+      return to_remove;
+    }
+    if (to_remove < trim_max * 1.5) {
+      dout(10) << __func__ << " trim to " << get_trim_to() << " would only trim " << to_remove
+             << " > paxos_service_trim_max, limiting to " << trim_max
+             << dendl;
+      return trim_max;
+    }
+    const version_t new_trim_max = (trim_max + to_remove) / 2;
+    const uint64_t trim_max_multiplier = g_conf().get_val<uint64_t>("paxos_service_trim_max_multiplier");
+    if (trim_max_multiplier) {
+      return std::min(new_trim_max, trim_max * trim_max_multiplier);
+    } else {
+      return new_trim_max;
+    }
+  }();
+  trim_to = get_first_committed() + to_remove;
 
   dout(10) << __func__ << " trimming to " << trim_to << ", " << to_remove << " states" << dendl;
   MonitorDBStore::TransactionRef t = paxos.get_pending_transaction();
-- 
2.47.3