# source:doc/theses/mubeen_zulfiqar_MMath/allocator.tex@58d471f

arm-ehjacob/cs343-translationnew-ast-unique-expr
Last change on this file since 58d471f was 58d471f, checked in by m3zulfiq <m3zulfiq@…>, 9 months ago

Added writing points for each chapter of Mubeen's thesis.

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1\chapter{Allocator}
2
3====================
4
5Writing Points:
6
7Objective of uHeapLmmm.
8Design philosophy.
9Background and previous design of uHeapLmmm.
10
11Distributed design of uHeapLmmm.
12----- SHOULD WE GIVE IMPLEMENTATION DETAILS HERE? -----
13> figure.
15
16The new features added to uHeapLmmm (incl. malloc_size routine)
17CFA alloc interface with examples.
18> Why did we need it?
20----- SHOULD WE GIVE PERFORMANCE AND USABILITY COMPARISON OF DIFFERENT INTERFACES THAT WE TRIED? -----
21
22Performance evaluation using u-benchmark suite.
23
24====================
25
26\newpage
27\paragraph{Design 1: Decentralized}
28Fixed number of heaps: shard the heap into N heaps each with a bump-area allocated from the sbrk area.
29Kernel threads (KT) are assigned to the N heaps.
30When KTs $\le$ N, the heaps are uncontented.
31When KTs $>$ N, the heaps are contented.
32By adjusting N, this approach reduces storage at the cost of speed due to contention.
33In all cases, a thread acquires/releases a lock, contented or uncontented.
34\begin{cquote}
35\centering
36\input{AllocDS1}
37\end{cquote}
38Problems: need to know when a KT is created and destroyed to know when to create/delete the KT's heap.
39On KT deletion, its heap freed-storage needs to be distributed somewhere.
40
41\paragraph{Design 2: Centralized}
42
43One heap, but lower bucket sizes are N-shared across KTs.
44This design leverages the fact that 95\% of allocation requests are less than 512 bytes and there are only 3--5 different request sizes.
45When KTs $\le$ N, the important bucket sizes are uncontented.
46When KTs $>$ N, the free buckets are contented.
47Therefore, threads are only contending for a small number of buckets, which are distributed among them to reduce contention.
48\begin{cquote}
49\centering
50\input{AllocDS2}
51\end{cquote}
52Problems: need to know when a kernel thread (KT) is created and destroyed to know when to assign a shared bucket-number.
53When no thread is assigned a bucket number, its free storage is unavailable.
54It is possible to use sharing and stealing techniques to share/find unused storage, when a free list is unused or empty.
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