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Cacol: a zero overhead and non-intrusive double caching mitigation system

Todeschi, Grégoire and Djomgwe Teabe, Boris and Tchana, Alain and Hagimont, Daniel Cacol: a zero overhead and non-intrusive double caching mitigation system. (2020) Future Generation Computer Systems, 106. 14-21. ISSN 0167-739X

(Document in English)

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Official URL: https://doi.org/10.1016/j.future.2019.11.035


In a virtualized server, a page cache (which caches I/O data) is managed in both the hypervisor and the guest Operating System (OS). This leads to a well-known issue called double caching. Double caching is the presence of the same data in both the hypervisor page cache and guest OS page caches. Some experiments we performed show that almost 64% of the hypervisor page cache content is also present in guest page caches. Therefore, double caching is a huge source of memory waste in virtualized servers, particularly when I/O disk-intensive workloads are executed (which is common in today’s data centers). Knowing that memory is the limiting resource for workload consolidation, double caching is a critical issue. This paper presents a novel solution (called Cacol) to avoid double caching. Unlike existing solutions, Cacol is not intrusive as it does not require guest OS modification and induces very little performance overhead for user applications. We implemented Cacol in KVM hypervisor, a very popular virtualization system. We evaluated Cacol and compared it with Linux default solutions. The results confirm the advantages (no guest modification and no overhead) of Cacol against existing solutions.

Item Type:Article
HAL Id:hal-02894310
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut National de la Recherche en Informatique et en Automatique - INRIA (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Université de Toulouse > Université Toulouse - Jean Jaurès - UT2J (FRANCE)
Université de Toulouse > Université Toulouse 1 Capitole - UT1 (FRANCE)
Other partners > Université Côte d'Azur (FRANCE)
Laboratory name:
Deposited On:24 Jun 2020 15:06

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