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copied!<p>This chip has an MMU, so Linux is likely using it to manage memory. Maybe just enabling it introduces some performance hit. Also, Linux uses a lazy memory allocation strategy, only assigning memory pages to a process when it first hits it. If you're copying a big chunk of memory, the MMU will generate page faults to ask the kernel to allocate a page while inside your loop. On a low-end processor, all these context switches cause cache flushes and introduce a noticeable slowdown.</p> <p>If your system is small enough, try an MMU-less version of Linux (like <a href="http://www.uclinux.org/" rel="noreferrer">uClinux</a>). Maybe it would let you use a cheaper chip with similar performance. On embedded systems, every penny counts.</p> <p><strong>update:</strong> Some extra details:</p> <p>Every Linux process gets it's own memory mappings, At first this include only the kernel and (maybe) executable code. All the rest of the linear 4GB (on 32bit) seems available, but there's no RAM pages assigned to them. As soon as you read or write an unallocated memory address, the MMU signals a page fault and switches to the kernel. The kernel sees that it still has lots of free RAM pages, so picks one, assigns it to the faulted point and returns to your code, which finishes the interrupted instruction. The very next one won't fail because the whole page (typically 4KB) is already assigned; but a few iterations later, it will hit another non-assigned space, and the MMU will invoke the kernel again.</p>

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