整理了手頭上幾本書中關(guān)于資源和內(nèi)存管理的章節(jié)
<Understanding the linux kenel
第三版> 8.1.7 the buddy system Buddy算法, 解決內(nèi)存碎片問題. 張貼書本原文如下：
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The
technique adopted by Linux to solve the external fragmentation problem
is based on the well-known buddy system
algorithm. All free page frames are grouped into 11 lists of blocks
that contain groups of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, and 1024
contiguous page frames, respectively. The largest request of 1024 page
frames corresponds to a chunk of 4 MB of contiguous RAM. The physical
address of the first page frame of a block is a multiple of the group
sizefor example, the initial address of a 16-page-frame block is a
multiple of 16 x 212 (212 = 4,096, which is the
regular page size).
We'll
show how the algorithm works through a simple example:
Assume there is a request for a group of 256 contiguous
page frames (i.e., one megabyte). The algorithm checks first to see
whether a free block in the 256-page-frame list exists. If there is no
such block, the algorithm looks for the next larger blocka free block in
the 512-page-frame list. If such a block exists, the kernel allocates
256 of the 512 page frames to satisfy the request and inserts the
remaining 256 page frames into the list of free 256-page-frame blocks.
If there is no free 512-page block, the kernel then looks for the next
larger block (i.e., a free 1024-page-frame block). If such a block
exists, it allocates 256 of the 1024 page frames to satisfy the request,
inserts the first 512 of the remaining 768 page frames into the list of
free 512-page-frame blocks, and inserts the last 256 page frames into
the list of free 256-page-frame blocks. If the list of 1024-page-frame
blocks is empty, the algorithm gives up and signals an error condition.
The reverse operation, releasing blocks of page frames,
gives rise to the name of this algorithm. The kernel attempts to merge
pairs of free buddy blocks of size b
together into a single block of size 2b.
Two blocks are considered buddies if:
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Both
blocks have the same size, say b.
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They are located in contiguous physical addresses.
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The physical address of the first page frame of the
first block is a multiple of 2 x b x 212.
The algorithm is iterative; if it succeeds in merging
released blocks, it doubles b and tries
again so as to create even bigger blocks
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<Modern
C++ design 泛型編程與設(shè)計(jì)模式> Chapter 4 small object allocation
本書討論的是loki庫。第4章探討了小對(duì)象的內(nèi)存分配
<STL源碼解析> 2.2 STL空間分配器
翻譯by 侯捷
SGI的STL實(shí)現(xiàn)中，allocator的實(shí)現(xiàn)例子。
二級(jí)分配器：大于128byte交給一個(gè)分配器，直接分配內(nèi)存。小數(shù)據(jù)塊交給次級(jí)分配器。
次級(jí)分配器用一個(gè)freelist數(shù)組維護(hù)可分配的小塊內(nèi)存區(qū)域。freelist數(shù)組中的項(xiàng)是一個(gè)固定內(nèi)存大小的鏈表。freelist中的項(xiàng)
這
里用了一個(gè)小技巧（union)
union obj {
union obj* free_list_link;
char
client_data[1];
}
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這個(gè)既可用于空閑列表節(jié)點(diǎn)，又能作為數(shù)據(jù)指針(強(qiáng)制轉(zhuǎn)換)， 這樣就可以節(jié)省信息記錄的空間。
詳細(xì)說明參考原書
<
游戲編程精粹1> 1.6 通用的基于句柄的資源管理器 該文章實(shí)現(xiàn)HandleMgr模板類實(shí)現(xiàn)不同類型資源的管理器.handle為整數(shù)值
基本思路
- vector<DATA>存放實(shí)際數(shù)據(jù),
vector儲(chǔ)存magic number, FreeVector儲(chǔ)存數(shù)據(jù)vector中的空閑索引值
- Acquire根據(jù)
handl值返回?cái)?shù)據(jù)指針(引用計(jì)數(shù)+1)， Release釋放data( 引用計(jì)數(shù)減1 ）
技巧1：
利用空結(jié)構(gòu)實(shí)現(xiàn)類型匹配（STL內(nèi)經(jīng)常用這個(gè)技巧）
struct tagTexture {}
typedef Handle<tagTexture> HTexture
技巧2：資源釋放時(shí)不需要析構(gòu)，只需要把相應(yīng)index加入空閑列表。分配時(shí)重用該對(duì)象，重新初始化值，可以提高效率。
技巧3：一般資源管理器類作為Singleton
擴(kuò)展1：為標(biāo)準(zhǔn)功能增加自動(dòng)引用計(jì)數(shù)（參考智能指針的實(shí)現(xiàn)？）
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游戲編程精粹1> 1.9 基于幀的內(nèi)存分配 by steven ranck
思路：棧方式（后進(jìn)先出）的內(nèi)存分配器。預(yù)先分配大塊內(nèi)存，然后按棧順序分配和釋放內(nèi)存。
僅適用于分配，釋放有嚴(yán)格順序的資源（如關(guān)卡資源）
<游戲編程精粹1> 1.1 技巧：所謂的數(shù)據(jù)繼承
對(duì)于不變的對(duì)象屬性，具體類用引用指向這些固定屬性，而不是繼承。
因?yàn)閮H通過對(duì)象繼承，每個(gè)對(duì)象都有這些固定屬性的拷貝，浪費(fèi)空間。
Sprite（速度，滿血值，攻擊力） <-- SpriteInstance( 對(duì)sprite引用, 位置，當(dāng)前生命值）