From 88639859dbd9a62267d949d3fd1eae3028d802c6 Mon Sep 17 00:00:00 2001
From: Derek Bruening <bruening@google.com>
Date: Wed, 25 May 2016 02:04:04 +0000
Subject: Add working set base runtime library

Summary:
Adds the base runtime library for the working set tool.
Adds slowpath code for updating the shadow memory.

To be added in the future:
+ Scan memory and report the total size.
+ Take samples for intermediate values.

Reviewers: aizatsky

Subscribers: kubabrecka, vitalybuka, zhaoqin, kcc, eugenis, llvm-commits

Differential Revision: http://reviews.llvm.org/D20485

llvm-svn: 270650
---
 compiler-rt/lib/esan/working_set.cpp | 90 ++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 compiler-rt/lib/esan/working_set.cpp

(limited to 'compiler-rt/lib/esan/working_set.cpp')

diff --git a/compiler-rt/lib/esan/working_set.cpp b/compiler-rt/lib/esan/working_set.cpp
new file mode 100644
index 00000000000..3cee6155b2a
--- /dev/null
+++ b/compiler-rt/lib/esan/working_set.cpp
@@ -0,0 +1,90 @@
+//===-- working_set.cpp ---------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of EfficiencySanitizer, a family of performance tuners.
+//
+// This file contains working-set-specific code.
+//===----------------------------------------------------------------------===//
+
+#include "working_set.h"
+#include "esan.h"
+#include "esan_flags.h"
+#include "esan_shadow.h"
+
+// We shadow every cache line of app memory with one shadow byte.
+// - The highest bit of each shadow byte indicates whether the corresponding
+//   cache line has ever been accessed.
+// - The lowest bit of each shadow byte indicates whether the corresponding
+//   cache line was accessed since the last sample.
+// - The other bits can be used either for a single working set snapshot
+//   between two consecutive samples, or an aggregate working set snapshot
+//   over multiple sample periods (future work).
+// We live with races in accessing each shadow byte.
+typedef unsigned char byte;
+
+namespace __esan {
+
+// See the shadow byte layout description above.
+static const u32 TotalWorkingSetBitIdx = 7;
+static const u32 CurWorkingSetBitIdx = 0;
+static const byte ShadowAccessedVal =
+  (1 << TotalWorkingSetBitIdx) | (1 << CurWorkingSetBitIdx);
+
+void processRangeAccessWorkingSet(uptr PC, uptr Addr, SIZE_T Size,
+                                  bool IsWrite) {
+  if (Size == 0)
+    return;
+  SIZE_T I = 0;
+  uptr LineSize = getFlags()->cache_line_size;
+  // As Addr+Size could overflow at the top of a 32-bit address space,
+  // we avoid the simpler formula that rounds the start and end.
+  SIZE_T NumLines = Size / LineSize +
+    // Add any extra at the start or end adding on an extra line:
+    (LineSize - 1 + Addr % LineSize + Size % LineSize) / LineSize;
+  byte *Shadow = (byte *)appToShadow(Addr);
+  // Write shadow bytes until we're word-aligned.
+  while (I < NumLines && (uptr)Shadow % 4 != 0) {
+    if ((*Shadow & ShadowAccessedVal) != ShadowAccessedVal)
+      *Shadow |= ShadowAccessedVal;
+    ++Shadow;
+    ++I;
+  }
+  // Write whole shadow words at a time.
+  // Using a word-stride loop improves the runtime of a microbenchmark of
+  // memset calls by 10%.
+  u32 WordValue = ShadowAccessedVal | ShadowAccessedVal << 8 |
+    ShadowAccessedVal << 16 | ShadowAccessedVal << 24;
+  while (I + 4 <= NumLines) {
+    if ((*(u32*)Shadow & WordValue) != WordValue)
+      *(u32*)Shadow |= WordValue;
+    Shadow += 4;
+    I += 4;
+  }
+  // Write any trailing shadow bytes.
+  while (I < NumLines) {
+    if ((*Shadow & ShadowAccessedVal) != ShadowAccessedVal)
+      *Shadow |= ShadowAccessedVal;
+    ++Shadow;
+    ++I;
+  }
+}
+
+void initializeWorkingSet() {
+  // The shadow mapping assumes 64 so this cannot be changed.
+  CHECK(getFlags()->cache_line_size == 64);
+}
+
+int finalizeWorkingSet() {
+  // FIXME NYI: we need to add memory scanning to report the total lines
+  // touched, and later add sampling to get intermediate values.
+  Report("%s is not finished: nothing yet to report\n", SanitizerToolName);
+  return 0;
+}
+
+} // namespace __esan
-- 
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