Skip to main content
main-content

Tipp

Weitere Artikel dieser Ausgabe durch Wischen aufrufen

01.03.2015 | Ausgabe 3/2015

The Journal of Supercomputing 3/2015

DASC-DIR: a low-overhead coherence directory for many-core processors

Zeitschrift:
The Journal of Supercomputing > Ausgabe 3/2015
Autoren:
Alberto Ros, Manuel E. Acacio

Abstract

Current trends point toward future many-core processors being implemented using the hardware-managed, implicitly addressed, coherent caches memory model. With this memory model, all on-chip storage is used for private and shared caches that are kept coherent by hardware. Communication between cores is performed by writing to and reading from shared memory, and a scalable point-to-point interconnection network is in charge of transmitting messages. Cache coherence in this context is guaranteed by means of a directory-based protocol. Unfortunately, it has been previously shown that the directory structure required to keep track of sharers can restrict the scalability of these designs due its excessive area or energy requirements, or for a compressed directory, the increased coherence traffic that in some cases it could cause. On the other hand, in many-core architectures, memory blocks are commonly assigned to the banks of a NUCA shared cache by following a physical mapping. This mapping assigns blocks to cache banks in a round-robin fashion, thus neglecting the distance between the cores that more frequently access every block and the corresponding NUCA bank for the block. This issue impacts both cache access latency and the amount of on-chip network traffic generated and causes that some area- and energy-efficient compressed directories significantly increase the number of messages per coherence event, which finally translates into degraded performance. In this work we propose an efficient and low-overhead coherence directory which is built around two main ingredients: the first is the use of the distance-aware round-robin mapping policy, an OS-managed policy which tries to map the pages accessed by a core to its closest (local) bank, at the same time it introduces an upper bound on the deviation of the distribution of memory pages among cache banks, which lessens the number of off-chip accesses. The second is the utilization of a very compressed directory structure which takes advantage of this mapping policy to represent sharers in a very compact way without increasing coherence network traffic. Simulation results for a 32-core architecture demonstrate that compared to a full-map directory using the typical round-robin physical mapping policy, our proposal drastically reduces the size of the directory structure (and thus, its area and energy requirements); at the same time, it does not increase coherence network traffic and 6 % average savings in execution time are achieved.

Bitte loggen Sie sich ein, um Zugang zu diesem Inhalt zu erhalten

Sie möchten Zugang zu diesem Inhalt erhalten? Dann informieren Sie sich jetzt über unsere Produkte:

Springer Professional "Wirtschaft"

Online-Abonnement

Mit Springer Professional "Wirtschaft" erhalten Sie Zugriff auf:

  • über 58.000 Bücher
  • über 300 Zeitschriften

aus folgenden Fachgebieten:

  • Bauwesen + Immobilien
  • Business IT + Informatik
  • Finance + Banking
  • Management + Führung
  • Marketing + Vertrieb
  • Versicherung + Risiko




Testen Sie jetzt 30 Tage kostenlos.

Springer Professional "Technik"

Online-Abonnement

Mit Springer Professional "Technik" erhalten Sie Zugriff auf:

  • über 50.000 Bücher
  • über 380 Zeitschriften

aus folgenden Fachgebieten:

  • Automobil + Motoren
  • Bauwesen + Immobilien
  • Business IT + Informatik
  • Elektrotechnik + Elektronik
  • Energie + Umwelt
  • Maschinenbau + Werkstoffe




Testen Sie jetzt 30 Tage kostenlos.

Springer Professional "Wirtschaft+Technik"

Online-Abonnement

Mit Springer Professional "Wirtschaft+Technik" erhalten Sie Zugriff auf:

  • über 69.000 Bücher
  • über 500 Zeitschriften

aus folgenden Fachgebieten:

  • Automobil + Motoren
  • Bauwesen + Immobilien
  • Business IT + Informatik
  • Elektrotechnik + Elektronik
  • Energie + Umwelt
  • Finance + Banking
  • Management + Führung
  • Marketing + Vertrieb
  • Maschinenbau + Werkstoffe
  • Versicherung + Risiko

Testen Sie jetzt 30 Tage kostenlos.

Literatur
Über diesen Artikel

Weitere Artikel der Ausgabe 3/2015

The Journal of Supercomputing 3/2015 Zur Ausgabe

Premium Partner

    Bildnachweise