Multi-channel symmetric server SMP technology and its application

SMP English is all called symmetrical multi-processing, meaning "symmetric multiprocessing" refers to the collection of a set of processors on a computer-that is, multiple CPUs, shared memory subsystems between CPUs, and bus structures. It is a widely used parallel technology in the relative asymmetric and multi processing technology.

In this architecture, a computer is no longer made up of a single CPU, while multiple processors run a single copy of the operating system and share memory and other resources on one computer. Although multiple CPUs are used at the same time, they behave like a single computer from a management standpoint. The system distributes task queues symmetrically across multiple CPUs, thus greatly improving the data processing capability of the whole system. All processors have equal access to memory, I/O, and external interrupts. In symmetric multiprocessing systems, system resources are shared by all CPUs in the system, and workloads can be distributed evenly over all available processors.

SMP applications

The current SMP technology is mainly used in the RISC server camp of the multi-channel minicomputer, X86 Server Camp multi-channel processing system and the use of a part of virtual CPU technology to achieve a single CPU (or multiple CPUs) virtual multi-channel.

We usually see the dual-Channel CPU system, which is the most common one of symmetric multi-processing systems, commonly referred to as "2-way symmetric multi-processing", which in ordinary business, home applications do not have much practical use, but in professional production, such as 3DMax Studio, Photoshop and other software applications have achieved very good performance, is a good partner to build low-cost workstations. With the improvement of users ' application level, it is very difficult to meet the requirement of actual application, so the server vendors use symmetric multiprocessing system to solve this contradiction. In the domestic market this type of processor typically 4 or 8 of the main, a few are 16 processors. But in general, the SMP structure of the machine scalability is poor, it is difficult to do more than 100 multiprocessor, the general is generally 8 to 16, but this for most users are enough.

The advantage of this machine is that it is used in a way that is not the same as the computer or workstation, the change in programming is relatively small, the original computer workstation program if you want to transplant to the SMP machine to use, the change is relatively easy. The SMP structure has a poor model availability. Because 4 or 8 processors share an operating system and a single memory, the entire machine is completely paralyzed once the operating system becomes problematic. And because of the poor scalability of the machine, it is not easy to protect the user's investment. But this kind of model technology is more mature, the corresponding software is also more, so now the domestic market launched a large number of parallel machine is this kind. The most common symmetric multiprocessing systems in PC servers typically use 2, 4, 6, or 8-way processors. Currently, UNIX servers can support up to 64 CPU systems, such as Sun's product enterprise 10000. The most critical technology in SMP systems is how to better solve the problem of communication and coordination among multiple processors.

SMP Build conditions

To build SMP systems, the first and foremost point is the need for appropriate CPUs to match. We usually see the CPU is a single use, so we can not see what difference they have, but, in fact, supporting the SMP function is not without conditions, random take a few CPUs to be able to build a multiple processing system that is Arabian. To achieve SMP functionality, the CPUs we use must have the following requirements:

1. Internal APIC (Advanced programmable Interrupt controllers) unit must be built inside the CPU. The core of the Intel Multi-processing specification is the use of the Advanced Programmable Interrupt controller (Advanced programmable Interrupt controllers--apics). The CPU completes communication between them by sending interrupts to each other. By giving interrupts additional actions (actions), different CPUs can be controlled to some degree. Each CPU has its own APIC (becoming the local APIC of that CPU), and there is an I/O APIC to handle interrupts caused by I/O devices, which are installed on the motherboard, but APIC on each CPU is essential, Otherwise, interrupt coordination between multiple CPUs cannot be handled.

2, the same product model, the same type of CPU core. For example, although the Xeon and Hao Dragons are each built with APIC units, it is not possible to build SMP systems together, and even if they belong to the CPU core of the Xeon series or the Hao long series, and they belong to the same development platform, they cannot build SMP systems--because their instructions are not exactly the same, APIC Interrupt coordination is also very different.

3, the exact same frequency of operation. If you want to build dual-Xeon or dual-hao long system, you must have two 2.8GHz or two 3.0GHz processors, can not use a 2.8GHz, another 3.0GHz to build, otherwise the system will not be normal light.

4. Keep the same product serial number as possible. Even the same frequency processors at the same core can cause incredible problems due to the different production batches. Two production batches of CPUs running as a dual processor, it is possible that one CPU burden is too high, and the other is very small, unable to perform maximum performance, or worse, may cause the panic, therefore, should choose the same batch of production processor to build SMP system.