• # Quid du POWER ?

    Posté par . En réponse au journal Ça sent pas bon chez Intel ?. Évalué à 4.

    Si le POWER n'a pas été cité, pourrait-il être concerné ?

    D'après ce que j'ai compris, le POWER utilise l'ERAT (Effective to Real Address Translation) et le TLB dans la translation d'adresse.

    http://www.redbooks.ibm.com/Redbooks.nsf/RedbookAbstracts/tips0956.html?Open

    The IBM POWER7 processor

    Several capabilities and features of the POWER7 processor are key to system optimization. POWER7 offers the following most important, yet simple features for performance tuning:

    • Multiple page size support feature

    Power Architecture supports multiple virtual memory page sizes, which in turn, provide performance benefits to an application because of hardware efficiencies that are associated with larger page sizes. Large pages provide several technical advantages such as the following examples:

    • Reduced page faults and Translation Lookaside Buffer (TLB) misses

    A single large page that is being constantly referenced remains in memory, eliminating the possibility of swapping out several small pages.

    • Unhindered data prefetching

    A large page enables unhindered data prefetch, which is constrained by page boundaries.

    • Increased TLB Reach

    This feature saves space in the TLB by holding one translation entry instead of n entries, which increases the amount of memory that can be accessed by an application without incurring hardware translation delays.

    • Increased Effective to Real Address Translation (ERAT) Reach

    ERAT on IBM POWER is a first-level and fully associative translation cache that can go directly from effective to real address. Effective addresses are the addresses used by the software, and real addresses refer to the physical memory that is assigned to the software by the system. Both the ERAT and the TLB are involved in translating addresses. Large pages also improve the efficiency and coverage of this translation cache.

    Une comparaison avait été faite entre le power8 et intel sur les aspects de TLB :

    https://www.anandtech.com/show/10435/assessing-ibms-power8-part-1/3

    Le TLB est plus gros sur le power, si on en vienait à devoir le flusher, les impacts pourraient-ils être plus importants ?

    Ce sera intéressant d'observer le discours d'IBM sur le sujet...le silence ou bien le marketing pour brandir un avantage concurrentiel.

    Pour l'heure, l'action d'intel ne baisse pas vraiment...