Changes between Version 66 and Version 67 of WikiStart

Timestamp:

Jan 22, 2020, 4:16:38 PM (3 years ago)

Author:

alain

Comment:

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WikiStart

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 This document describes the general principles of ALMOS-MKH, which is an operating system targeting manycore architectures with CC-NUMA (Coherent Cache, Non Uniform Memory Access) shared address space, such as the TSAR architecture which can support up to 1024 32-bit MIPS cores. ALMOS-MKH also targets INTEL based multi-core servers using 64-bit I86 cores.
 
-Targeted architectures are assumed to be clustered, with one or several cores, and a physical memory bank per cluster. These architectures are supposed to support POSIX-compliant  multi-threaded parallel applications.
+Targeted architectures are assumed to be clustered, with one or several cores, and one physical memory bank per cluster. These architectures are supposed to support POSIX-compliant  multi-threaded parallel applications.
 
 ALMOS-MKH inherited from the ALMOS system, developed by Ghassan Almaless. The general principles of the ALMOS system are described in his thesis.
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 A first version of ALMOS-MKH, and in particular the distributed file system and the RPC communication mechanism were developed by Mohamed Karaoui. The general principles of the proposed Multi-Kernel approach are described in his thesis. This system was called ALMOS-MK (without H).
 
-ALMOS-MKH is based on the "Multi-Kernel" approach to ensure scalability, and support the distribution of system services. In this approach, each cluster of the architecture contains an instance of the kernel. Each instance controls the local resources (memory and computing cores). These multiple instances cooperate with each other to give applications the image of a single system controlling all resources. They communicate with each other using both (i) the client / server model, sending a remote procedure call  (RPC) to a remote cluster for a complex service, (ii) the shared memory paradigm, making direct access to remote memory when required. 
+ALMOS-MKH is based on the "Multi-Kernel" approach to ensure scalability, and support the distribution of system services. In this approach, each cluster of the architecture contains an instance of the kernel. Each instance controls the local resources (memory and computing cores). These multiple instances cooperate with each other to give applications the image of a single system controlling all resources. They communicate with each other using both (i) the client / server model, sending a remote procedure call  (RPC) to a remote cluster for a complex service, (ii) the shared memory paradigm, making direct read/write access to remote memory when required. 
 
 The main ALMOS-MKH specific feature is the following: the physical address space is supposed to be distributed between the clusters, and the MSB bits of the physical address  are supposed to define the target cluster. In a physical address, the LSB bits contain the '''lpa''' (Local Physical Address), and the MSB bits define the '''cxy''' (Cluster Identifier).  The physical address space is therefore described as a two levels array M[cxy][lpa]. To enforce locality, a kernel instance  can use a normal pointer '''ptr''' to access the local physical memory. But, to access the physical memory of a remote cluster (cxy), it must use the specific remote access functions ''remote_read(cxy,ptr)'' and ''remote_write(cxy,ptr)'', where ''ptr'' is the local pointer in the target cluster. This (cxy,ptr) couple is called an ''extended pointer''.