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