add constants for shared (GUI/core) -dbcache settings

- adds nDefaultDbCache, nMaxDbCache and nMinDbCache in txdb.h

src/init.cpp

@@ -196,7 +196,7 @@ std::string HelpMessage(HelpMessageMode hmm)
     strUsage += "  -testnet               " + _("Use the test network") + "\n";
     strUsage += "  -pid=<file>            " + _("Specify pid file (default: bitcoind.pid)") + "\n";
     strUsage += "  -gen                   " + _("Generate coins (default: 0)") + "\n";
-    strUsage += "  -dbcache=<n>           " + _("Set database cache size in megabytes (default: 100)") + "\n";
+    strUsage += "  -dbcache=<n>           " + strprintf(_("Set database cache size in megabytes (%d to %d, default: %d)"), nMinDbCache, nMaxDbCache, nDefaultDbCache) + "\n";
     strUsage += "  -timeout=<n>           " + _("Specify connection timeout in milliseconds (default: 5000)") + "\n";
     strUsage += "  -proxy=<ip:port>       " + _("Connect through SOCKS proxy") + "\n";
     strUsage += "  -socks=<n>             " + _("Select SOCKS version for -proxy (4 or 5, default: 5)") + "\n";
@@ -776,9 +776,11 @@ bool AppInit2(boost::thread_group& threadGroup)
     }
 
     // cache size calculations
-    size_t nTotalCache = GetArg("-dbcache", 100) << 20;
-    if (nTotalCache < (1 << 22))
-        nTotalCache = (1 << 22); // total cache cannot be less than 4 MiB
+    size_t nTotalCache = (GetArg("-dbcache", nDefaultDbCache) << 20);
+    if (nTotalCache < (nMinDbCache << 20))
+        nTotalCache = (nMinDbCache << 20); // total cache cannot be less than nMinDbCache
+    else if (nTotalCache > (nMaxDbCache << 20))
+        nTotalCache = (nMaxDbCache << 20); // total cache cannot be greater than nMaxDbCache
     size_t nBlockTreeDBCache = nTotalCache / 8;
     if (nBlockTreeDBCache > (1 << 21) && !GetBoolArg("-txindex", false))
         nBlockTreeDBCache = (1 << 21); // block tree db cache shouldn't be larger than 2 MiB

src/qt/forms/optionsdialog.ui

@@ -53,17 +53,7 @@
           </widget>
          </item>
          <item>
-          <widget class="QSpinBox" name="databaseCache">
-           <property name="toolTip">
-            <string>Set database cache size in megabytes (default: 25)</string>
-           </property>
-           <property name="maximum">
-            <number>1024</number>
-           </property>
-           <property name="value">
-            <number>25</number>
-           </property>
-          </widget>
+          <widget class="QSpinBox" name="databaseCache"/>
          </item>
          <item>
           <widget class="QLabel" name="databaseCacheUnitLabel">

src/qt/optionsdialog.cpp

@@ -14,8 +14,9 @@
 #include "monitoreddatamapper.h"
 #include "optionsmodel.h"
 
+#include "main.h" // for CTransaction::nMinTxFee
 #include "netbase.h"
-#include "main.h"
+#include "txdb.h" // for -dbcache defaults
 
 #include <QDir>
 #include <QIntValidator>
@@ -34,7 +35,8 @@ OptionsDialog::OptionsDialog(QWidget *parent) :
     GUIUtil::restoreWindowGeometry("nOptionsDialogWindow", this->size(), this);
 
     /* Main elements init */
-    ui->databaseCache->setMaximum(sizeof(void*) > 4 ? 4096 : 1024);
+    ui->databaseCache->setMinimum(nMinDbCache);
+    ui->databaseCache->setMaximum(nMaxDbCache);
 
     /* Network elements init */
 #ifndef USE_UPNP

src/qt/optionsmodel.cpp

@@ -14,6 +14,7 @@
 #include "init.h"
 #include "main.h"
 #include "net.h"
+#include "txdb.h" // for -dbcache defaults
 #ifdef ENABLE_WALLET
 #include "wallet.h"
 #include "walletdb.h"
@@ -84,7 +85,7 @@ void OptionsModel::Init()
 #endif
 
     if (!settings.contains("nDatabaseCache"))
-        settings.setValue("nDatabaseCache", 100);
+        settings.setValue("nDatabaseCache", nDefaultDbCache);
     if (!SoftSetArg("-dbcache", settings.value("nDatabaseCache").toString().toStdString()))
         strOverriddenByCommandLine += "-dbcache ";
 

src/txdb.h

@@ -18,6 +18,13 @@ class CBigNum;
 class CCoins;
 class uint256;
 
+// -dbcache default (MiB)
+static const int nDefaultDbCache = 100;
+// max. -dbcache in (MiB)
+static const int nMaxDbCache = sizeof(void*) > 4 ? 4096 : 1024;
+// min. -dbcache in (MiB)
+static const int nMinDbCache = 4;
+
 /** CCoinsView backed by the LevelDB coin database (chainstate/) */
 class CCoinsViewDB : public CCoinsView
 {