Prudent Memory Reclamation in Procrastination-Based Synchronization

Prasad, Aravinda and Gopinath, K (2016) Prudent Memory Reclamation in Procrastination-Based Synchronization. In: 21st International Conference on Architectural Support for Programming Languages and Operating Systems, APR 02-06, 2016, Atlanta, GA, pp. 99-112.

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Abstract

Procrastination is the fundamental technique used in synchronization mechanisms such as Read-Copy-Update (RCU) where writers, in order to synchronize with readers, defer the freeing of an object until there are no readers referring to the object. The synchronization mechanism determines when the deferred object is safe to reclaim and when it is actually reclaimed. Hence, such memory reclamations are completely oblivious of the memory allocator state. This induces poor memory allocator performance, for instance, when the reclamations are ill-timed. Furthermore, deferred objects provide hints about the future that inform memory regions that are about to be freed. Although useful, hints are not exploited as deferred objects are not ``visible'' to memory allocators. We introduce Prudence, a dynamic memory allocator, that is tightly integrated with the synchronization mechanism to ensure visibility of deferred objects to the memory allocator. Such an integration enables Prudence to (i) identify the safe time to reclaim deferred objects' memory, (ii) have an inclusive view of the allocated, free and about-to-be-freed objects, and (iii) exploit optimizations based on the hints about the future during important state transitions. Our evaluation in the Linux kernel shows that Prudence integrated with RCU performs 3.9 x to 28 x better in microbenchmarks compared to SLUB, a recent memory allocator in the Linux kernel. It also improves the overall performance perceptibly (4%-18%) for a mix of widely used synthetic and application benchmarks. Further, it performs better (up to 98%) in terms of object hits in caches, object cache churns, slab churns, peak memory usage and total fragmentation, when compared with the SLUB allocator.

Item Type:	Conference Proceedings
Publication:	OPERATING SYSTEMS REVIEW
Additional Information:	Copy right for this article belongs to the ASSOC COMPUTING MACHINERY, 2 PENN PLAZA, STE 701, NEW YORK, NY 10121-0701 USA
Department/Centre:	Division of Electrical Sciences > Computer Science & Automation
Date Deposited:	03 Dec 2016 09:42
Last Modified:	03 Dec 2016 09:42
URI:	http://eprints.iisc.ac.in/id/eprint/55364

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