CODEWITHSUNDEEP
linux-kernelarm
user435739
user435739

Reputation:

Linux ARM CONFIG_SMP=y on a uniprocessor system

What is the difference in linux booting sequence later, between a linux compiled with CONFIG_SMP=y and one with CONFIG_SMP=n

Upvotes: 1

Views: 1305

Answers (2)

Joe Kul
Joe Kul

Reputation: 2534

There are various low-level differences if you run a single-CPU system with CONFIG_SMP=y kernel. These will result in larger binary and degraded performance.

Roughly speaking: with SMP=n, the SMP synchronization primitives (widespread in kernel) compile to nothing, no instructions are generated. Similarly, PERCPU activities compile to nothing.

With SMP on, compile produces instructions which are executed e.g. to acquire and release locks. Similarly, PERCPU loops, which index from 1 to 1, are created around various kernel actions. IIRC, I saw increase in boot time and degraded dd micro-benchmark performance, roughly 10%.

Upvotes: 2

Jiminion
Jiminion

Reputation: 5168

If yes, it enables multiple processors (if present) to be run during startup. So, no difference.

Upvotes: -1

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