Correct units for "-dbcache" and "-prune"

All dbcache-related values in the code are measured in MiB (not in
megabytes, MB) or in bytes.
The GUI "-prune" values in GB are translated to the node values in MiB
correctly. The maximum of the "-prune" QSpinBox is not limited by the
default value of 99 (GB).
Also, this improves log readability.

src/init.cpp

@@ -346,7 +346,7 @@ void SetupServerArgs()
     gArgs.AddArg("-conf=<file>", strprintf("Specify configuration file. Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-datadir=<dir>", "Specify data directory", false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-dbbatchsize", strprintf("Maximum database write batch size in bytes (default: %u)", nDefaultDbBatchSize), true, OptionsCategory::OPTIONS);
-    gArgs.AddArg("-dbcache=<n>", strprintf("Set database cache size in megabytes (%d to %d, default: %d)", nMinDbCache, nMaxDbCache, nDefaultDbCache), false, OptionsCategory::OPTIONS);
+    gArgs.AddArg("-dbcache=<n>", strprintf("Set database cache size in MiB (%d to %d, default: %d)", nMinDbCache, nMaxDbCache, nDefaultDbCache), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-debuglogfile=<file>", strprintf("Specify location of debug log file. Relative paths will be prefixed by a net-specific datadir location. (-nodebuglogfile to disable; default: %s)", DEFAULT_DEBUGLOGFILE), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-feefilter", strprintf("Tell other nodes to filter invs to us by our mempool min fee (default: %u)", DEFAULT_FEEFILTER), true, OptionsCategory::OPTIONS);
     gArgs.AddArg("-includeconf=<file>", "Specify additional configuration file, relative to the -datadir path (only useable from configuration file, not command line)", false, OptionsCategory::OPTIONS);

src/qt/forms/optionsdialog.ui

@@ -121,7 +121,7 @@
          <item>
           <widget class="QLabel" name="databaseCacheUnitLabel">
            <property name="text">
-            <string>MB</string>
+            <string>MiB</string>
            </property>
            <property name="textFormat">
             <enum>Qt::PlainText</enum>

src/qt/guiconstants.h

@@ -52,4 +52,7 @@ static const int MAX_URI_LENGTH = 255;
 #define QAPP_APP_NAME_TESTNET "Bitcoin-Qt-testnet"
 #define QAPP_APP_NAME_REGTEST "Bitcoin-Qt-regtest"
 
+/* One gigabyte (GB) in bytes */
+static constexpr uint64_t GB_BYTES{1000000000};
+
 #endif // BITCOIN_QT_GUICONSTANTS_H

src/qt/intro.cpp

@@ -10,6 +10,7 @@
 #include <qt/intro.h>
 #include <qt/forms/ui_intro.h>
 
+#include <qt/guiconstants.h>
 #include <qt/guiutil.h>
 
 #include <interfaces/node.h>
@@ -21,7 +22,6 @@
 
 #include <cmath>
 
-static const uint64_t GB_BYTES = 1000000000LL;
 /* Total required space (in GB) depending on user choice (prune, not prune) */
 static uint64_t requiredSpace;
 

src/qt/optionsdialog.cpp

@@ -10,6 +10,7 @@
 #include <qt/forms/ui_optionsdialog.h>
 
 #include <qt/bitcoinunits.h>
+#include <qt/guiconstants.h>
 #include <qt/guiutil.h>
 #include <qt/optionsmodel.h>
 
@@ -37,10 +38,6 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
     /* Main elements init */
     ui->databaseCache->setMinimum(nMinDbCache);
     ui->databaseCache->setMaximum(nMaxDbCache);
-    static const uint64_t GiB = 1024 * 1024 * 1024;
-    static const uint64_t nMinDiskSpace = MIN_DISK_SPACE_FOR_BLOCK_FILES / GiB +
-                          (MIN_DISK_SPACE_FOR_BLOCK_FILES % GiB) ? 1 : 0;
-    ui->pruneSize->setMinimum(nMinDiskSpace);
     ui->threadsScriptVerif->setMinimum(-GetNumCores());
     ui->threadsScriptVerif->setMaximum(MAX_SCRIPTCHECK_THREADS);
     ui->pruneWarning->setVisible(false);
@@ -161,6 +158,10 @@ void OptionsDialog::setModel(OptionsModel *_model)
         mapper->toFirst();
 
         updateDefaultProxyNets();
+
+        // Prune values are in GB to be consistent with intro.cpp
+        static constexpr uint64_t nMinDiskSpace = (MIN_DISK_SPACE_FOR_BLOCK_FILES / GB_BYTES) + (MIN_DISK_SPACE_FOR_BLOCK_FILES % GB_BYTES) ? 1 : 0;
+        ui->pruneSize->setRange(nMinDiskSpace, _model->node().getAssumedBlockchainSize());
     }
 
     /* warn when one of the following settings changes by user action (placed here so init via mapper doesn't trigger them) */

src/qt/optionsmodel.cpp

@@ -9,6 +9,7 @@
 #include <qt/optionsmodel.h>
 
 #include <qt/bitcoinunits.h>
+#include <qt/guiconstants.h>
 #include <qt/guiutil.h>
 
 #include <interfaces/node.h>
@@ -92,9 +93,9 @@ void OptionsModel::Init(bool resetSettings)
         settings.setValue("bPrune", false);
     if (!settings.contains("nPruneSize"))
         settings.setValue("nPruneSize", 2);
-    // Convert prune size to MB:
-    const uint64_t nPruneSizeMB = settings.value("nPruneSize").toInt() * 1000;
-    if (!m_node.softSetArg("-prune", settings.value("bPrune").toBool() ? std::to_string(nPruneSizeMB) : "0")) {
+    // Convert prune size from GB to MiB:
+    const uint64_t nPruneSizeMiB = (settings.value("nPruneSize").toInt() * GB_BYTES) >> 20;
+    if (!m_node.softSetArg("-prune", settings.value("bPrune").toBool() ? std::to_string(nPruneSizeMiB) : "0")) {
         addOverriddenOption("-prune");
     }
 

src/validation.h

@@ -201,14 +201,14 @@ static const unsigned int NODE_NETWORK_LIMITED_MIN_BLOCKS = 288;
 static const signed int DEFAULT_CHECKBLOCKS = 6;
 static const unsigned int DEFAULT_CHECKLEVEL = 3;
 
-// Require that user allocate at least 550MB for block & undo files (blk???.dat and rev???.dat)
+// Require that user allocate at least 550 MiB for block & undo files (blk???.dat and rev???.dat)
 // At 1MB per block, 288 blocks = 288MB.
 // Add 15% for Undo data = 331MB
 // Add 20% for Orphan block rate = 397MB
 // We want the low water mark after pruning to be at least 397 MB and since we prune in
 // full block file chunks, we need the high water mark which triggers the prune to be
 // one 128MB block file + added 15% undo data = 147MB greater for a total of 545MB
-// Setting the target to > than 550MB will make it likely we can respect the target.
+// Setting the target to >= 550 MiB will make it likely we can respect the target.
 static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
 
 /**

test/functional/feature_pruning.py

@@ -320,7 +320,7 @@ class PruneTest(BitcoinTestFramework):
         if has_block(3):
             raise AssertionError("blk00003.dat is still there, should be pruned by now")
 
-        # stop node, start back up with auto-prune at 550MB, make sure still runs
+        # stop node, start back up with auto-prune at 550 MiB, make sure still runs
         self.stop_node(node_number)
         self.start_node(node_number, extra_args=["-prune=550"])