From 46c887b77eb2f8a3c356e75b340c1c2286a9cfbb Mon Sep 17 00:00:00 2001
From: Stefan Weil <sw@weilnetz.de>
Date: Wed, 3 May 2017 09:49:23 +0200
Subject: [PATCH] genericvector: Fix minimum size

Commit 907de5995f698e2a01da25fa09f8cadaf31a095f tried to improve
GenericVector, but missed a case where vectors with less than
kDefaultVectorSize were allocated. This resulted in additional
alloc / free operations.

Commit a28b2a033df10010bba9c1f49d6410ad69b3cdde (before memory optimization)
oem 0: total heap usage: 739,238 allocs, 739,237 frees, 161,699,214 bytes allocated
oem 1: total heap usage: 690,182 allocs, 690,175 frees, 144,470,400 bytes allocated
oem 2: total heap usage: 728,213 allocs, 728,206 frees, 182,885,824 bytes allocated

Commit fd3f8f9b2d8c9ebf72b20a9d254a8e5c6900461e without genericvector change
oem 0: total heap usage: 738,980 allocs, 738,979 frees, 161,697,150 bytes allocated
oem 1: total heap usage: 690,182 allocs, 690,175 frees, 144,470,400 bytes allocated
oem 2: total heap usage: 728,213 allocs, 728,206 frees, 182,885,824 bytes allocated
=> Improvements for oem 0, no change for oem 1 and oem 2.

Commit fd3f8f9b2d8c9ebf72b20a9d254a8e5c6900461e
oem 0: total heap usage: 772,648 allocs, 772,647 frees, 160,083,901 bytes allocated
oem 1: total heap usage: 748,591 allocs, 748,584 frees, 143,581,672 bytes allocated
oem 2: total heap usage: 764,796 allocs, 764,789 frees, 181,212,197 bytes allocated
=> Less bytes allocated, but more allocs / frees = bad for performance.

Commit fd3f8f9b2d8c9ebf72b20a9d254a8e5c6900461e with this patch
oem 0: total heap usage: 677,537 allocs, 677,536 frees, 160,444,634 bytes allocated
oem 1: total heap usage: 653,812 allocs, 653,805 frees, 143,423,008 bytes allocated
oem 2: total heap usage: 670,029 allocs, 670,022 frees, 181,517,760 bytes allocated
=> Improvements for all three cases.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
 ccutil/genericvector.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ccutil/genericvector.h b/ccutil/genericvector.h
index dfc70f1afa..4dee34d178 100644
--- a/ccutil/genericvector.h
+++ b/ccutil/genericvector.h
@@ -658,6 +658,7 @@ template <typename T>
 void GenericVector<T>::reserve(int size) {
   if (size_reserved_ >= size || size <= 0)
     return;
+  if (size < kDefaultVectorSize) size = kDefaultVectorSize;
   T* new_array = new T[size];
   for (int i = 0; i < size_used_; ++i)
     new_array[i] = data_[i];