From 20299f87cb7a155c64e3fcbe747bcbf5591eaa23 Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Thu, 8 Apr 2021 02:21:27 +0300
Subject: [PATCH] mdbx: minor refine `get_reasonable_db_maxsize()`.

Change-Id: I5d654940a325c0c3966a59a37615820587c52c78
---
 src/core.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/src/core.c b/src/core.c
index b8e64c6e..8b79837e 100644
--- a/src/core.c
+++ b/src/core.c
@@ -10532,20 +10532,15 @@ __cold static intptr_t get_reasonable_db_maxsize(intptr_t *cached_result) {
     *cached_result = (intptr_t)((size_t)total_ram_pages * 207 >> 7) * pagesize;
 
     /* Round to the nearest human-readable granulation. */
-    for (int i = 10; i < MDBX_WORDBITS - 1; i += 10) {
-      const size_t unit = (size_t)1 << i;
+    for (size_t unit = MEGABYTE; unit; unit <<= 5) {
       const size_t floor = floor_powerof2(*cached_result, unit);
       const size_t ceil = ceil_powerof2(*cached_result, unit);
-      if (*cached_result - floor < ceil - *cached_result ||
-          ceil > MAX_MAPSIZE) {
-        if (*cached_result - floor > (size_t)*cached_result / 16)
-          break;
-        *cached_result = floor;
-      } else {
-        if (ceil - *cached_result > (size_t)*cached_result / 16)
-          break;
-        *cached_result = ceil;
-      }
+      const size_t threshold = (size_t)*cached_result >> 4;
+      const bool down =
+          *cached_result - floor < ceil - *cached_result || ceil > MAX_MAPSIZE;
+      if (threshold < (down ? *cached_result - floor : ceil - *cached_result))
+        break;
+      *cached_result = down ? floor : ceil;
     }
   }
   return *cached_result;