randomx: optional 2 MB large pages for the cache, dataset and scratchpads

RandomX reads its 256 MB cache, 2 GB dataset and per-VM scratchpads at random,
so most accesses miss the TLB on 4 KB pages. Requesting 2 MB pages recovers
roughly a tenth of the hash rate. Each allocation tries large pages first and
falls back to normal pages when the pool is not reserved, so nothing regresses
when hugepages are unavailable. -nolargepages opts out, and the diagnostics
report which allocations got large pages.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 0a961bf..a01bdee 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -127,6 +127,8 @@ static void PrintUsage()
     printf("  /stratumbridgeport=N       (default 3333; listen on 127.0.0.1)\n");
     printf("  /solomine\n");
     printf("  /genproclimit=N            (mining threads; 0 or absent = every core but one)\n");
+    printf("  /nolargepages              (do not ask for 2 MB pages for the RandomX\n");
+    printf("                              cache, dataset and scratchpads)\n");
     printf("  /checkblocks=N             (blocks re-verified at startup, default 288, 0 = all)\n");
     printf("\n");
     printf("Pool operator announcement:\n");
@@ -230,6 +232,11 @@ static void ParseStartupArguments(int argc, char* argv[])
     if (!strCheckBlocks.empty())
         nCheckBlocksOnLoad = atoi(strCheckBlocks.c_str());
 
+    // Must be read before LoadBlockIndex(), which is what first calls
+    // RandomXInit() and fixes how the cache is allocated.
+    if (arg(argc,argv,"/nolargepages") || arg(argc,argv,"-nolargepages"))
+        fRandomXLargePages = false;
+
     // /genproclimit=N -- threads to hash with. 0 or absent means automatic,
     // which is every core but one. Named after Bitcoin's own option so it reads
     // familiarly to anyone who has run one of these before.