From 297d831192b797157851125a71af4deec9a4773c Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew.noyes@snowflake.com>
Date: Tue, 19 Apr 2022 11:22:35 -0700
Subject: [PATCH] Put guard pages next to fast alloc memory (#6885)
* Put guard pages next to fast alloc memory
I verified that we can now detect #6753 without creating tons of
threads.
* Use pageSize instead of 4096
* Don't include mmapInternal for windows
---
flow/FastAlloc.cpp | 2 +-
flow/Platform.actor.cpp | 27 +++++++++++++++++++++------
flow/Platform.h | 2 +-
3 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/flow/FastAlloc.cpp b/flow/FastAlloc.cpp
index 262d1b017c..dd6f68c542 100644
--- a/flow/FastAlloc.cpp
+++ b/flow/FastAlloc.cpp
@@ -519,7 +519,7 @@ void FastAllocator<Size>::getMagazine() {
--g_allocation_tracing_disabled;
}
#endif
- block = (void**)::allocate(magazine_size * Size, false);
+ block = (void**)::allocate(magazine_size * Size, /*allowLargePages*/ false, /*includeGuardPages*/ true);
#endif
// void** block = new void*[ magazine_size * PSize ];
diff --git a/flow/Platform.actor.cpp b/flow/Platform.actor.cpp
index c07ff01bca..4661c0c6ea 100644
--- a/flow/Platform.actor.cpp
+++ b/flow/Platform.actor.cpp
@@ -2037,7 +2037,22 @@ static void enableLargePages() {
#endif
}
-static void* allocateInternal(size_t length, bool largePages) {
+#ifndef _WIN32
+static void* mmapInternal(size_t length, int flags, bool guardPages) {
+ if (guardPages) {
+ constexpr size_t pageSize = 4096;
+ length += 2 * pageSize; // Map enough for the guard pages
+ void* resultWithGuardPages = mmap(nullptr, length, PROT_READ | PROT_WRITE, flags, -1, 0);
+ mprotect(resultWithGuardPages, pageSize, PROT_NONE); // left guard page
+ mprotect((void*)(uintptr_t(resultWithGuardPages) + length - pageSize), pageSize, PROT_NONE); // right guard page
+ return (void*)(uintptr_t(resultWithGuardPages) + pageSize);
+ } else {
+ return mmap(nullptr, length, PROT_READ | PROT_WRITE, flags, -1, 0);
+ }
+}
+#endif
+
+static void* allocateInternal(size_t length, bool largePages, bool guardPages) {
#ifdef _WIN32
DWORD allocType = MEM_COMMIT | MEM_RESERVE;
@@ -2052,31 +2067,31 @@ static void* allocateInternal(size_t length, bool largePages) {
if (largePages)
flags |= MAP_HUGETLB;
- return mmap(nullptr, length, PROT_READ | PROT_WRITE, flags, -1, 0);
+ return mmapInternal(length, flags, guardPages);
#elif defined(__APPLE__) || defined(__FreeBSD__)
int flags = MAP_PRIVATE | MAP_ANON;
- return mmap(nullptr, length, PROT_READ | PROT_WRITE, flags, -1, 0);
+ return mmapInternal(length, flags, guardPages);
#else
#error Port me!
#endif
}
static bool largeBlockFail = false;
-void* allocate(size_t length, bool allowLargePages) {
+void* allocate(size_t length, bool allowLargePages, bool includeGuardPages) {
if (allowLargePages)
enableLargePages();
void* block = ALLOC_FAIL;
if (allowLargePages && !largeBlockFail) {
- block = allocateInternal(length, true);
+ block = allocateInternal(length, true, includeGuardPages);
if (block == ALLOC_FAIL)
largeBlockFail = true;
}
if (block == ALLOC_FAIL)
- block = allocateInternal(length, false);
+ block = allocateInternal(length, false, includeGuardPages);
// FIXME: SevWarnAlways trace if "close" to out of memory
diff --git a/flow/Platform.h b/flow/Platform.h
index 020544178f..272c8e3588 100644
--- a/flow/Platform.h
+++ b/flow/Platform.h
@@ -284,7 +284,7 @@ std::string epochsToGMTString(double epochs);
void setMemoryQuota(size_t limit);
-void* allocate(size_t length, bool allowLargePages);
+void* allocate(size_t length, bool allowLargePages, bool includeGuardPages);
void setAffinity(int proc);