Alexander Halbuer (M.Sc.)

Wissenschaftlicher Mitarbeiter

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Telefon

0511 762 19729

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E-mail

halbuer@sra.uni-hannover.de

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Adresse

Appelstraße 4
30167 Hannover

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Gebäude

3703

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Raum

Raum 119

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Appelstraße 4 Raum 119

Projects

ParPerOS: Parallel Persistency OS (DFG: LO 1719/8-1 and DI 2840/2-1)

In ParPerOS, we examine new abstractions for unified but efficient and optionally crash-consistent low-level memory management for data objects in heterogeneous memory systems that consist of volatile, persistent, distributed and other types of main memory.

Publications

2024

DIMES Workshop Best Paper Award
The New Costs of Physical Memory Fragmentation

Alexander Halbuer, Illia Ostapyshyn, Lukas Steiner, Lars Wrenger, Matthias Jung, Christian Dietrich, Daniel LohmannProceedings of the 2nd Workshop on Disruptive Memory Systems (SOSP-DIMES '24)Association for Computing Machinery2024Best Paper Award.
PDF Details 10.1145/3698783.3699378 [BibTex]

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BibTex Entry

@inproceedings{halbuer:24:dimes,
author = {Alexander Halbuer and Illia Ostapyshyn and Lukas Steiner and Lars Wrenger and Matthias Jung and Christian Dietrich and Daniel Lohmann},
booktitle = {Proceedings of the 2nd Workshop on Disruptive Memory Systems (SOSP-DIMES '24)},
doi = {10.1145/3698783.3699378},
entrysubtype = {Workshop},
location = {Austin, Texas, USA},
publisher = {Association for Computing Machinery},
title = {The New Costs of Physical Memory Fragmentation},
year = {2024},
}

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2023

DIMES Workshop
Morsels: Explicit Virtual Memory Objects

Alexander Halbuer, Christian Dietrich, Florian Rommel, Daniel LohmannProceedings of the 1st Workshop on Disruptive Memory SystemsAssociation for Computing Machinery2023.
PDF Details Slides 10.1145/3609308.3625267 [BibTex]

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BibTex Entry

@inproceedings{halbuer:23:dimes,
author = {Alexander Halbuer and Christian Dietrich and Florian Rommel and Daniel Lohmann},
booktitle = {Proceedings of the 1st Workshop on Disruptive Memory Systems},
date = {2023-10},
doi = {10.1145/3609308.3625267},
entrysubtype = {Workshop},
location = {Koblenz, Germany},
month = {October},
publisher = {Association for Computing Machinery},
series = {DIMES '23},
title = {Morsels: Explicit Virtual Memory Objects},
year = {2023},
}

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USENIX Conference A Distinguished Artifact Award
LLFree: Scalable and Optionally-Persistent Page-Frame Allocation

Lars Wrenger, Florian Rommel, Alexander Halbuer, Christian Dietrich, Daniel Lohmann2023 USENIX Annual Technical Conference (USENIX '23)USENIX Association2023Distinguished Artifact Award.
PDF Details Slides [BibTex]

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BibTex Entry

@inproceedings{wrenger:23:atc,
location = {Boston, MA},
author = {Wrenger, Lars and Rommel, Florian and Halbuer, Alexander and Dietrich, Christian and Lohmann, Daniel},
booktitle = {2023 USENIX Annual Technical Conference (USENIX '23)},
entrysubtype = {Conference},
isbn = {978-1-939133-35-9},
month = {jul},
pages = {897–914},
publisher = {USENIX Association},
title = {{LLFree}: Scalable and {Optionally-Persistent} {Page-Frame} Allocation},
url = {https://www.usenix.org/conference/atc23/presentation/wrenger},
year = {2023},
}

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Teaching

Supervised Theses

Open Theses Topics

Shared Virtual-Memory Objects for Disaggregated Memory with Limited Coherency

CXL will bring shared, disaggregated memory with limited coherency. We will utilize the available coherency to build efficient synchronization for the remaining memory in software.

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Typ

Masterarbeit

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Status

offen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

Running Theses

Dynamic Metadata Management for Virtual-Memory Objects

Hash tables allow for memory-efficient handling of metadata, particularly in scenarios where numerous properties remain unused for extended periods of time. Nevertheless, existing implementations are not optimized for workloads characterized by a large number of small objects and stringent low-latency requirements.

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Typ

Bachelorarbeit

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Status

laufend

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Alex Alfonso Trigo

Multi-Target Virtual-Memory Objects

Paging has established as goto solution for memory virtualization, but actual implementations differ. Multiple sychronized views could fill the gap to allow direct sharing between different domains.

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Typ

Bachelor-/Masterarbeit

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Status

laufend

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Nils Fuhler

Transparent Huge Pages for Virtual-Memory Objects

Morsels are currently limited to a single, unified page size per object (4 KiB, 2 MiB, or 1 GiB), which must be defined at creation time. To better accommodate real-world application needs, a more flexible implementation that supports variable page sizes is required.

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Typ

Bachelorarbeit

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Status

reserviert

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

Finished Student Theses

Databases on NVRAM

Bringing the advantages of non-volatile memory to database applications using the new morsel memory primitive as efficient abstraction layer.

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Typ

Bachelorarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Matthias Wormann (abgegeben: 02. Oct 2023)

Morsel Managment Layer: Making Morsels Actually Useful

Bringing the new morsel memory abstraction to applications.

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Darian Biastoch (abgegeben: 26. Oct 2023)

Efficient Serialization of Page-Table-Based Virtual Memory Objects

With the discontinuation of Intel Optane and persistent memory being rarely available in general, alternative solutions need to be considered. One approach is to persist virtual memory objects on disk when persistent memory is not available.

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Typ

Bachelorarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

Structured Design of LaTeX-Beamer Slides and their Presentation in Multi-Moniter Environments

Create and extend the software support for multi-monitor presentations and evaluate useful usage and application scenarios.

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Typ

Bachelorarbeit

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Status

abgeschlossen

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Supervisors

Björn Fiedler
Alexander Halbuer
Daniel Lohmann

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Bearbeiter

Simon Hermes

Huge Pages for Virtual-Memory Objects

Currently, Morsels only support 4-KiB pages, but with larger page sizes the management overhead could be further reduced and the average memory access could be sped up, due to faster page-table walks and an increased TLB coverage.

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Typ

Bachelorarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Marko Bolowski (abgegeben: 18. Mar 2024)

Efficient Copy-on-Write for Virtual-Memory Objects

Implementing classical, full-featured COW with multiple nesting levels would introduce substantial management overhead on the operating system side. Our goal with Morsels is to eliminate this overhead while retaining limited COW functionality.

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Pasha Fistanto (abgegeben: 02. May 2024)

Optimizing Memory Metadata: Dynamic Allocation of Struct Pages in the Linux Kernel

Dynamically allocate a struct page in cases where it is needed and omit the memory overhead in cases where it is not.

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Lars Wrenger
Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Paul Aumann (abgegeben: 14. Jun 2024)

Page Eviction for Shared Virtual-Memory Objects

The translation lookaside buffer (TLB) caches present page table entries, so that pages can not be unmapped by simply clearing the related page table entry. However, page eviction is vital for implementing advanced features like swapping and huge-page merging. [PDF]

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Tim Hollmann (abgegeben: 03. Jul 2024)

Efficient Swapping of Shared Virtual-Memory Objects

By design, morsels exist in main memory without being just an intermediate representation of a file. However, for some applications it would be desirable to store objects on a disk in order to persist its data during reboots or to cope with limited main memory.

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Typ

Bachelorarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Julian-Dominik Helmsen (abgegeben: 05. Aug 2024)

Enhancing Energy Efficiency with Advanced DRAM Management in Linux

Modern computer systems face a significant challenge in managing physical memory efficiently, especially in the context of energy consumption. Specifically, the DRAM (Dynamic Random-Access Memory) components in these systems consume a considerable amount of energy due to their constant refresh requirements. [PDF]

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Alexander Halbuer
Christian Dietrich
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Illia Ostapyshyn (abgegeben: 01. Nov 2024)

Own Thesis

Self-Contained Virtual-Memory Areas for Non-Volatile RAM in the Linux Kernel

Implement the basic abstraction for self-contained virtual-address-space areas in Linux, by which we want to ease the allocation, the sharing, and the management of huge amounts of memory. [PDF]

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Typ

Masterarbeit

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Status

abgeschlossen

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Supervisors

Lars Wrenger
Florian Rommel
Christian Dietrich
Daniel Lohmann

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Project

ParPerOS

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Bearbeiter

Alexander Halbuer (abgegeben: 16. Nov 2022)