reduce cache sizes so that default maxsigcache size is same as Bitcoin

Bitcoin allocates 32M for signature caching by default, split
between a signature cache and a script validity cache (see
Core #10192). Since 0.14 we have added an additional 32M for
rangeproof caching *and* an additional 32M for surjectionproof
caching.

These cache entries cost a bit over 32 bytes, so these are room
for a million entries....or 4Gb of rangeproofs and 300M of
surjection proofs.

Presumably we did not intend to triple memory usage relative to
Core to deal with some champagne problem in which our mempool is
overfilled ten times with pure rangeproofs. So put the total
default cache size back to 32M. This should have no performance
hit under realistic circumstances and should reduce CI OOM failures.

On my system we now use 50M rather than 110M during the fedpeg
test; we still use 18M that Core does not by having three additional
global secp contexts (one in blind.cpp, one in pegins.cpp, one in
confidential_validation.cpp) but we can settle that in a future
commit.

src/script/sigcache.cpp

@@ -115,9 +115,9 @@ void InitSignatureCache()
 {
     // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
     // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 4), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
     size_t nElems = signatureCache.setup_bytes(nMaxCacheSize);
-    LogPrintf("Using %zu MiB out of %zu/2 requested for signature cache, able to store %zu elements\n",
+    LogPrintf("Using %zu MiB out of %zu/4 requested for signature cache, able to store %zu elements\n",
             (nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
 }
 
@@ -152,9 +152,9 @@ void InitRangeproofCache()
 {
     // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
     // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE)), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE/4)), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
     size_t nElems = rangeProofCache.setup_bytes(nMaxCacheSize);
-    LogPrintf("Using %zu MiB out of %zu requested for rangeproof cache, able to store %zu elements\n",
+    LogPrintf("Using %zu MiB out of %zu/4 requested for rangeproof cache, able to store %zu elements\n",
             (nElems*sizeof(uint256)) >>20, nMaxCacheSize>>20, nElems);
 }
 
@@ -163,9 +163,9 @@ void InitSurjectionproofCache()
 {
     // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
     // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE)), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE/4)), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
     size_t nElems = surjectionProofCache.setup_bytes(nMaxCacheSize);
-    LogPrintf("Using %zu MiB out of %zu requested for surjectionproof cache, able to store %zu elements\n",
+    LogPrintf("Using %zu MiB out of %zu/4 requested for surjectionproof cache, able to store %zu elements\n",
             (nElems*sizeof(uint256)) >>20, nMaxCacheSize>>20, nElems);
 }
 

src/validation.cpp

@@ -1514,9 +1514,9 @@ void InitScriptExecutionCache() {
     g_scriptExecutionCacheHasher.Write(nonce.begin(), 32);
     // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
     // setup_bytes creates the minimum possible cache (2 elements).
-    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
+    size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 4), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
     size_t nElems = g_scriptExecutionCache.setup_bytes(nMaxCacheSize);
-    LogPrintf("Using %zu MiB out of %zu/2 requested for script execution cache, able to store %zu elements\n",
+    LogPrintf("Using %zu MiB out of %zu/4 requested for script execution cache, able to store %zu elements\n",
             (nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
 }