SERVER-23624 Allow wiredTigerCacheSizeGB to be specified as a float

4 files changed, 12 insertions, 6 deletions

diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.cpp
index 01aa0d3bbc1..fd16df07dcb 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.cpp
@@ -46,9 +46,9 @@ Status WiredTigerGlobalOptions::add(moe::OptionSection* options) {
     // WiredTiger storage engine options
     wiredTigerOptions.addOptionChaining("storage.wiredTiger.engineConfig.cacheSizeGB",
                                         "wiredTigerCacheSizeGB",
-                                        moe::Int,
+                                        moe::Double,
                                         "maximum amount of memory to allocate for cache; "
-                                        "defaults to 1/2 of physical RAM").validRange(1, 10000);
+                                        "defaults to 1/2 of physical RAM");
     wiredTigerOptions.addOptionChaining(
                           "storage.wiredTiger.engineConfig.statisticsLogDelaySecs",
                           "wiredTigerStatisticsLogDelaySecs",
@@ -107,7 +107,7 @@ Status WiredTigerGlobalOptions::store(const moe::Environment& params,
     // WiredTiger storage engine options
     if (params.count("storage.wiredTiger.engineConfig.cacheSizeGB")) {
         wiredTigerGlobalOptions.cacheSizeGB =
-            params["storage.wiredTiger.engineConfig.cacheSizeGB"].as<int>();
+            params["storage.wiredTiger.engineConfig.cacheSizeGB"].as<double>();
     }
     if (params.count("storage.syncPeriodSecs")) {
         wiredTigerGlobalOptions.checkpointDelaySecs =
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.h b/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.h
index 9e2307ff0fa..7d92c2fe986 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_global_options.h
@@ -50,7 +50,7 @@ public:
     Status add(moe::OptionSection* options);
     Status store(const moe::Environment& params, const std::vector<std::string>& args);
 
-    size_t cacheSizeGB;
+    double cacheSizeGB;
     size_t checkpointDelaySecs;
     size_t statisticsLogDelaySecs;
     std::string journalCompressor;
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
index 4d493077a3b..a3f6f5e8a95 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
@@ -318,8 +318,9 @@ int64_t WiredTigerUtil::getIdentSize(WT_SESSION* s, const std::string& uri) {
     return result.getValue();
 }
 
-size_t WiredTigerUtil::getCacheSizeMB(int requestedCacheSizeGB) {
+size_t WiredTigerUtil::getCacheSizeMB(double requestedCacheSizeGB) {
     double cacheSizeMB;
+    const double kMaxSizeCacheMB = 10 * 1000 * 1000;
     if (requestedCacheSizeGB == 0) {
         // Choose a reasonable amount of cache when not explicitly specified by user.
         // Set a minimum of 256MB, otherwise use 50% of available memory over 1GB.
@@ -329,6 +330,11 @@ size_t WiredTigerUtil::getCacheSizeMB(int requestedCacheSizeGB) {
     } else {
         cacheSizeMB = 1024 * requestedCacheSizeGB;
     }
+    if (cacheSizeMB > kMaxSizeCacheMB) {
+        log() << "Requested cache size: " << cacheSizeMB << "MB exceeds max; setting to "
+              << kMaxSizeCacheMB << "MB";
+        cacheSizeMB = kMaxSizeCacheMB;
+    }
     return static_cast<size_t>(cacheSizeMB);
 }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.h b/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
index 6f12bd54531..6227ae7852d 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.h
@@ -180,7 +180,7 @@ public:
      * Return amount of memory to use for the WiredTiger cache based on either the startup
      * option chosen or the amount of available memory on the host.
      */
-    static size_t getCacheSizeMB(int requestedCacheSizeGB);
+    static size_t getCacheSizeMB(double requestedCacheSizeGB);
 
     /**
      * Returns a WT_EVENT_HANDER with MongoDB's default handlers.