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Make span lifetime bucket bounds static constexpr. #305

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Make span lifetime bucket bounds static constexpr. #305

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47 changes: 23 additions & 24 deletions tcmalloc/central_freelist.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@
#include <cstdint>
#include <iostream>

#include "absl/algorithm/container.h"
#include "absl/base/attributes.h"
#include "absl/base/const_init.h"
#include "absl/base/internal/cycleclock.h"
Expand Down Expand Up @@ -155,7 +154,8 @@ class CentralFreeList {
first_nonempty_index_(0),
pages_per_span_(0),
nonempty_(),
use_all_buckets_for_few_object_spans_(false) {}
use_all_buckets_for_few_object_spans_(false),
lifetime_bucket_bounds_() {}

CentralFreeList(const CentralFreeList&) = delete;
CentralFreeList& operator=(const CentralFreeList&) = delete;
Expand Down Expand Up @@ -305,17 +305,6 @@ class CentralFreeList {
}

static constexpr size_t kLifetimeBuckets = 8;
static constexpr std::array<size_t, kLifetimeBuckets> kLifetimeBucketBounds =
[]() {
std::array<size_t, kLifetimeBuckets> bounds{};
static_assert(kLifetimeBuckets >= 2, "Buckets must be >= 2");
bounds[0] = 0;
bounds[1] = 1;
for (size_t i = 2; i < kLifetimeBuckets; ++i) {
bounds[i] = bounds[i - 1] * 10;
}
return bounds;
}();
using LifetimeHistogram = size_t[kLifetimeBuckets];

StatsCounter completed_spans_[kLifetimeBuckets];
Expand All @@ -325,9 +314,11 @@ class CentralFreeList {

int LifetimeBucketNum(absl::Duration duration) {
int64_t duration_ms = absl::ToInt64Milliseconds(duration);
auto it = absl::c_upper_bound(kLifetimeBucketBounds, duration_ms);
TC_CHECK_NE(it, kLifetimeBucketBounds.begin());
return it - kLifetimeBucketBounds.begin() - 1;
auto it = std::upper_bound(lifetime_bucket_bounds_,
lifetime_bucket_bounds_ + kLifetimeBuckets,
duration_ms);
TC_CHECK_NE(it, lifetime_bucket_bounds_);
return it - lifetime_bucket_bounds_ - 1;
}

// The followings are kept as a StatsCounter so that they can read without
Expand Down Expand Up @@ -375,6 +366,8 @@ class CentralFreeList {

bool use_all_buckets_for_few_object_spans_;

size_t lifetime_bucket_bounds_[kLifetimeBuckets];

// Tracks the number of long-lived spans moved to the long-lived section of
// nonempty_ per call to HandleLongLivedSpans.
StatsCounters<kSpanMoveStatBuckets> long_lived_spans_moved_;
Expand Down Expand Up @@ -409,6 +402,12 @@ inline void CentralFreeList<Forwarder>::Init(size_t size_class)
std::min<size_t>(absl::bit_width(objects_per_span_), kNumLists);

TC_ASSERT_LE(absl::bit_width(objects_per_span_), kSpanUtilBucketCapacity);

lifetime_bucket_bounds_[0] = 0;
lifetime_bucket_bounds_[1] = 1;
for (int i = 2; i < kLifetimeBuckets; ++i) {
lifetime_bucket_bounds_[i] = lifetime_bucket_bounds_[i - 1] * 10;
}
}

template <class Forwarder>
Expand Down Expand Up @@ -834,7 +833,7 @@ inline void CentralFreeList<Forwarder>::PrintSpanLifetimeStats(Printer& out) {
out.printf("class %3d [ %8zu bytes ] live spans: ", size_class_,
object_size_);
for (size_t i = 0; i < kLifetimeBuckets; ++i) {
out.printf("%3zu ms < %6zu", kLifetimeBucketBounds[i], lifetime_histo[i]);
out.printf("%3zu ms < %6zu", lifetime_bucket_bounds_[i], lifetime_histo[i]);
if (i < kLifetimeBuckets - 1) {
out.printf(",");
}
Expand All @@ -844,7 +843,7 @@ inline void CentralFreeList<Forwarder>::PrintSpanLifetimeStats(Printer& out) {
out.printf("class %3d [ %8zu bytes ] completed spans: ", size_class_,
object_size_);
for (size_t i = 0; i < kLifetimeBuckets; ++i) {
out.printf("%3zu ms < %6zu", kLifetimeBucketBounds[i],
out.printf("%3zu ms < %6zu", lifetime_bucket_bounds_[i],
completed_spans_[i].value());

if (i < kLifetimeBuckets - 1) {
Expand Down Expand Up @@ -938,19 +937,19 @@ inline void CentralFreeList<Forwarder>::PrintSpanLifetimeStatsInPbtxt(

for (size_t i = 0; i < kLifetimeBuckets; ++i) {
PbtxtRegion histogram = region.CreateSubRegion("span_lifetime_histogram");
histogram.PrintI64("lower_bound", kLifetimeBucketBounds[i]);
histogram.PrintI64("lower_bound", lifetime_bucket_bounds_[i]);
histogram.PrintI64("upper_bound", (i == kLifetimeBuckets - 1
? kLifetimeBucketBounds[i]
: kLifetimeBucketBounds[i + 1]));
? lifetime_bucket_bounds_[i]
: lifetime_bucket_bounds_[i + 1]));
histogram.PrintI64("value", lifetime_histo[i]);
}
for (size_t i = 0; i < kLifetimeBuckets; ++i) {
PbtxtRegion histogram =
region.CreateSubRegion("span_completed_lifetime_histogram");
histogram.PrintI64("lower_bound", kLifetimeBucketBounds[i]);
histogram.PrintI64("lower_bound", lifetime_bucket_bounds_[i]);
histogram.PrintI64("upper_bound", (i == kLifetimeBuckets - 1
? kLifetimeBucketBounds[i]
: kLifetimeBucketBounds[i + 1]));
? lifetime_bucket_bounds_[i]
: lifetime_bucket_bounds_[i + 1]));
histogram.PrintI64("value", completed_spans_[i].value());
}
}
Expand Down