# Changeset dbfae7b

Ignore:
Timestamp:
Mar 30, 2021, 8:40:23 AM (20 months ago)
Branches:
arm-eh, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum
Children:
a41e87b
Parents:
d0e80f61
Message:

add figures for design possibilities

Location:
doc/theses/mubeen_zulfiqar_MMath
Files:
 rd0e80f61 \chapter{Allocator} \newpage \paragraph{Design 1: Decentralized} Fixed number of heaps: shard the heap into N heaps each with a bump-area allocated from the sbrk area. Kernel threads (KT) are assigned to the N heaps. When KTs $\le$ N, the heaps are uncontented. When KTs $>$ N, the heaps are contented. By adjusting N, this approach reduces storage at the cost of speed due to contention. In all cases, a thread acquires/releases a lock, contented or uncontented. \begin{cquote} \centering \input{AllocDS1} \end{cquote} Problems: need to know when a KT is created and destroyed to know when to create/delete the KT's heap. On KT deletion, its heap freed-storage needs to be distributed somewhere. \paragraph{Design 2: Centralized} One heap, but lower bucket sizes are N-shared across KTs. This design leverages the fact that 95\% of allocation requests are less than 512 bytes and there are only 3--5 different request sizes. When KTs $\le$ N, the important bucket sizes are uncontented. When KTs $>$ N, the free buckets are contented. Therefore, threads are only contending for a small number of buckets, which are distributed among them to reduce contention. \begin{cquote} \centering \input{AllocDS2} \end{cquote} Problems: need to know when a kernel thread (KT) is created and destroyed to know when to assign a shared bucket-number. When no thread is assigned a bucket number, its free storage is unavailable. It is possible to use sharing and stealing techniques to share/find unused storage, when a free list is unused or empty.