From 1705d14b8fef5ebb826a74549d609c6ab6cb63f7 Mon Sep 17 00:00:00 2001
From: Siyuan Ren <netheril96@gmail.com>
Date: Fri, 6 May 2022 22:56:32 +0800
Subject: [PATCH] Allow overriding num shards by env variable.

---
 sources/file_table.cpp | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/sources/file_table.cpp b/sources/file_table.cpp
index 893d9504..d095a740 100644
--- a/sources/file_table.cpp
+++ b/sources/file_table.cpp
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <cstdlib>
 #include <limits>
 #include <queue>
 #include <string.h>
@@ -320,15 +321,11 @@ ShardedFileTableImpl::ShardedFileTableImpl(int version,
                                            unsigned iv_size,
                                            unsigned max_padding_size)
 {
-    unsigned num_shards = 8;
-    auto cpu_count = std::thread::hardware_concurrency();
-    if (cpu_count <= 2)
+    unsigned num_shards = 4;
+    const char* env_shards = std::getenv("SECUREFS_NUM_FILE_TABLE_SHARDS");
+    if (env_shards)
     {
-        num_shards = 2;
-    }
-    else
-    {
-        num_shards = std::min(64u, 1u << static_cast<unsigned>(std::ceil(std::log2(cpu_count))));
+        num_shards = std::max(2ul, std::strtoul(env_shards, nullptr, 0));
     }
     TRACE_LOG("Use %u shards of FileTableImpls.", num_shards);