Brief Announcement Hyaline : Fast and Transparent Memory - - PowerPoint PPT Presentation

Brief Announcement Hyaline: Fast and Transparent Memory Reclamation

Ruslan Nikolaev and Binoy Ravindran

rnikola@vt.edu, binoy@vt.edu

Systems Software Research Group Virginia Tech, USA

Memory Reclamation Problem

• Concurrent programming is hard

– Non-blocking (lock-free) data structures require special

treatment of deleted memory objects

– Garbage collectors are often impractical in C/C++

• Desirable properties for memory reclamation

– Non-blocking: protecting non-blocking data structures – Robust: bound memory usage even when threads are

stalled or preempted

– Transparent: avoid implicit assumptions about threads;

they can be created/deleted dynamically

Hyaline

• General idea

– Distributed reference counting, triggered only when

deleting objects

– Maintains multiple global lists of deleted objects – Each list is used by a subset of threads

Handle (Thread i) ... Handle (Thread j) NRef + HRef NRef NRef ... NRef NRef NRef NRef ≤ 0 Head [HRef, HPtr] New Head NRef NRef NRef ... (1) (2) (3)

Comparison

Scheme Performance Robust Transparent Extra Memory API complexity

Reference Counting Very Slow Yes Partially (swap) Double each pointer Intrusive Hazard Pointers Slow Yes No (deletion) 1 word Hard Epoch Based Reclamation Fast No No (deletion) 1 word Easy Hazard Eras Fast Yes No (deletion) 3 words Hard Interval Based Reclamation (2GEIBR) Fast Yes No (deletion) 3 words Medium Hyaline Very Fast No Yes 3 words Easy Hyaline-1 Very Fast No Almost 3 words Easy Hyaline-S Fast Yes Yes 3 words Medium Hyaline-1S Fast Yes Almost 3 words Medium

Evaluation

• >

25 50 75 100 125 1 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144

Threads Throughput (M ops/sec)

• >

Leak Memory Epoch Hyaline Hyaline−1 Hyaline−S Hyaline−1S IBR HE HP

• >

1000 2000 3000 1 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144

Threads Retired Objects per Operation

• >

Epoch IBR Hyaline Hyaline−1 Hyaline−S Hyaline−1S HE HP

• 0.10

0.15 0.20 0.25 1 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144

Threads Throughput (M ops/sec)

• Leak Memory

Epoch Hyaline Hyaline−1 Hyaline−S Hyaline−1S IBR

• 500

1000 1500 1 9 18 27 36 45 54 63 72 81 90 99 108 117 126 135 144

Threads Retired Objects per Operation

• Epoch

IBR Hyaline Hyaline−1 Hyaline−S Hyaline−1S

Bonsai Tree Hash Map Xeon E7-8880 v3 2.30 GHz, 72 cores

More details

• Code is open-source and available at:

– https://github.com/rusnikola/lfsmr

• Full paper is available as an arXiv report:

– https://arxiv.org/pdf/1905.07903.pdf

Thank you!