From 87acc2782fe49a8b57d19783f61ff8bc667db68d Mon Sep 17 00:00:00 2001
From: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Date: Sun, 8 Mar 2020 18:22:17 -0700
Subject: [PATCH] amputate span events history

Nobody used it in years. Abseil tcmalloc had it amputated years ago.
---
 src/central_freelist.cc |  3 ---
 src/page_heap.cc        |  8 --------
 src/span.cc             | 12 ------------
 src/span.h              | 14 --------------
 4 files changed, 37 deletions(-)

diff --git a/src/central_freelist.cc b/src/central_freelist.cc
index 01a7310..d064c2f 100644
--- a/src/central_freelist.cc
+++ b/src/central_freelist.cc
@@ -110,7 +110,6 @@ void CentralFreeList::ReleaseToSpans(void* object) {
   if (span->objects == NULL) {
     tcmalloc::DLL_Remove(span);
     tcmalloc::DLL_Prepend(&nonempty_, span);
-    Event(span, 'N', 0);
   }
 
   // The following check is expensive, so it is disabled by default
@@ -129,7 +128,6 @@ void CentralFreeList::ReleaseToSpans(void* object) {
   counter_++;
   span->refcount--;
   if (span->refcount == 0) {
-    Event(span, '#', 0);
     counter_ -= ((span->length<<kPageShift) /
                  Static::sizemap()->ByteSizeForClass(span->sizeclass));
     tcmalloc::DLL_Remove(span);
@@ -305,7 +303,6 @@ int CentralFreeList::FetchFromOneSpans(int N, void **start, void **end) {
     // Move to empty list
     tcmalloc::DLL_Remove(span);
     tcmalloc::DLL_Prepend(&empty_, span);
-    Event(span, 'E', 0);
   }
 
   *start = span->objects;
diff --git a/src/page_heap.cc b/src/page_heap.cc
index 7dd5646..44ad654 100644
--- a/src/page_heap.cc
+++ b/src/page_heap.cc
@@ -221,12 +221,10 @@ Span* PageHeap::Split(Span* span, Length n) {
   ASSERT(n < span->length);
   ASSERT(span->location == Span::IN_USE);
   ASSERT(span->sizeclass == 0);
-  Event(span, 'T', n);
 
   const int extra = span->length - n;
   Span* leftover = NewSpan(span->start + n, extra);
   ASSERT(leftover->location == Span::IN_USE);
-  Event(leftover, 'U', extra);
   RecordSpan(leftover);
   pagemap_.set(span->start + n - 1, span); // Update map from pageid to span
   span->length = n;
@@ -262,14 +260,12 @@ Span* PageHeap::Carve(Span* span, Length n) {
   const int old_location = span->location;
   RemoveFromFreeList(span);
   span->location = Span::IN_USE;
-  Event(span, 'A', n);
 
   const int extra = span->length - n;
   ASSERT(extra >= 0);
   if (extra > 0) {
     Span* leftover = NewSpan(span->start + n, extra);
     leftover->location = old_location;
-    Event(leftover, 'S', extra);
     RecordSpan(leftover);
 
     // The previous span of |leftover| was just splitted -- no need to
@@ -309,7 +305,6 @@ void PageHeap::Delete(Span* span) {
   span->sizeclass = 0;
   span->sample = 0;
   span->location = Span::ON_NORMAL_FREELIST;
-  Event(span, 'D', span->length);
   MergeIntoFreeList(span);  // Coalesces if possible
   IncrementalScavenge(n);
   ASSERT(stats_.unmapped_bytes+ stats_.committed_bytes==stats_.system_bytes);
@@ -379,7 +374,6 @@ void PageHeap::MergeIntoFreeList(Span* span) {
     span->start -= len;
     span->length += len;
     pagemap_.set(span->start, span);
-    Event(span, 'L', len);
   }
   Span* next = CheckAndHandlePreMerge(span, GetDescriptor(p+n));
   if (next != NULL) {
@@ -389,7 +383,6 @@ void PageHeap::MergeIntoFreeList(Span* span) {
     DeleteSpan(next);
     span->length += len;
     pagemap_.set(span->start + span->length - 1, span);
-    Event(span, 'R', len);
   }
 
   PrependToFreeList(span);
@@ -554,7 +547,6 @@ void PageHeap::RegisterSizeClass(Span* span, uint32 sc) {
   ASSERT(span->location == Span::IN_USE);
   ASSERT(GetDescriptor(span->start) == span);
   ASSERT(GetDescriptor(span->start+span->length-1) == span);
-  Event(span, 'C', sc);
   span->sizeclass = sc;
   for (Length i = 1; i < span->length-1; i++) {
     pagemap_.set(span->start+i, span);
diff --git a/src/span.cc b/src/span.cc
index 4d08964..eac43f4 100644
--- a/src/span.cc
+++ b/src/span.cc
@@ -42,23 +42,11 @@
 
 namespace tcmalloc {
 
-#ifdef SPAN_HISTORY
-void Event(Span* span, char op, int v = 0) {
-  span->history[span->nexthistory] = op;
-  span->value[span->nexthistory] = v;
-  span->nexthistory++;
-  if (span->nexthistory == sizeof(span->history)) span->nexthistory = 0;
-}
-#endif
-
 Span* NewSpan(PageID p, Length len) {
   Span* result = Static::span_allocator()->New();
   memset(result, 0, sizeof(*result));
   result->start = p;
   result->length = len;
-#ifdef SPAN_HISTORY
-  result->nexthistory = 0;
-#endif
   return result;
 }
 
diff --git a/src/span.h b/src/span.h
index ca3f710..7068893 100644
--- a/src/span.h
+++ b/src/span.h
@@ -93,24 +93,10 @@ struct Span {
   // Copies out and destroys iterator stored in span_iter_space.
   SpanSet::iterator ExtractSpanSetIterator();
 
-#undef SPAN_HISTORY
-#ifdef SPAN_HISTORY
-  // For debugging, we can keep a log events per span
-  int nexthistory;
-  char history[64];
-  int value[64];
-#endif
-
   // What freelist the span is on: IN_USE if on none, or normal or returned
   enum { IN_USE, ON_NORMAL_FREELIST, ON_RETURNED_FREELIST };
 };
 
-#ifdef SPAN_HISTORY
-void Event(Span* span, char op, int v = 0);
-#else
-#define Event(s,o,v) ((void) 0)
-#endif
-
 inline SpanPtrWithLength::SpanPtrWithLength(Span* s)
     : span(s),
       length(s->length) {