From 8607ff617c175dc4a7e436349bf6284758d5e4ea Mon Sep 17 00:00:00 2001
From: daan <daanl@outlook.com>
Date: Tue, 8 Sep 2020 17:16:31 -0700
Subject: [PATCH] add environment option mi_reserve_os_memory

---
 include/mimalloc.h |  1 +
 src/init.c         |  6 +++++-
 src/options.c      | 11 ++++++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/mimalloc.h b/include/mimalloc.h
index ea79a522..b980037c 100644
--- a/include/mimalloc.h
+++ b/include/mimalloc.h
@@ -304,6 +304,7 @@ typedef enum mi_option_e {
   mi_option_reset_decommits,
   mi_option_large_os_pages,         // implies eager commit
   mi_option_reserve_huge_os_pages,
+  mi_option_reserve_os_memory,
   mi_option_segment_cache,
   mi_option_page_reset,
   mi_option_abandoned_page_reset,
diff --git a/src/init.c b/src/init.c
index 48601637..bc17791b 100644
--- a/src/init.c
+++ b/src/init.c
@@ -478,7 +478,11 @@ void mi_process_init(void) mi_attr_noexcept {
   if (mi_option_is_enabled(mi_option_reserve_huge_os_pages)) {
     size_t pages = mi_option_get(mi_option_reserve_huge_os_pages);
     mi_reserve_huge_os_pages_interleave(pages, 0, pages*500);
-  }  
+  } 
+  if (mi_option_is_enabled(mi_option_reserve_os_memory)) {
+    long ksize = mi_option_get(mi_option_reserve_os_memory);
+    if (ksize > 0) mi_reserve_os_memory((size_t)ksize*KiB, true, true);
+  }
 }
 
 // Called when the process is done (through `at_exit`)
diff --git a/src/options.c b/src/options.c
index 7e565ea4..2dbc8b03 100644
--- a/src/options.c
+++ b/src/options.c
@@ -74,7 +74,8 @@ static mi_option_desc_t options[_mi_option_last] =
   { 0, UNINIT, MI_OPTION(reset_decommits) },     // reset uses MADV_FREE/MADV_DONTNEED
   #endif
   { 0, UNINIT, MI_OPTION(large_os_pages) },      // use large OS pages, use only with eager commit to prevent fragmentation of VMA's
-  { 0, UNINIT, MI_OPTION(reserve_huge_os_pages) },
+  { 0, UNINIT, MI_OPTION(reserve_huge_os_pages) },  // per 1GiB huge pages
+  { 0, UNINIT, MI_OPTION(reserve_os_memory)     },
   { 0, UNINIT, MI_OPTION(segment_cache) },       // cache N segments per thread
   { 1, UNINIT, MI_OPTION(page_reset) },          // reset page memory on free
   { 0, UNINIT, MI_OPTION(abandoned_page_reset) },// reset free page memory when a thread terminates
@@ -504,6 +505,14 @@ static void mi_option_init(mi_option_desc_t* desc) {
     else {
       char* end = buf;
       long value = strtol(buf, &end, 10);
+      if (desc->option == mi_option_reserve_os_memory) {
+        // this option is interpreted in KiB to prevent overflow of `long`
+        if (*end == 'K') { end++; }
+        else if (*end == 'M') { value *= KiB; end++; }
+        else if (*end == 'G') { value *= MiB; end++; }
+        else { value = (value + KiB - 1) / KiB; }
+        if (*end == 'B') { end++; }
+      }
       if (*end == 0) {
         desc->value = value;
         desc->init = INITIALIZED;