I realized that two things can be separated. One is whether DIAGNOSTIC turns on features that increase the size of memory allocations, which is my real concern. The other is whether the KMEM_SIZE and KMEM_REDZONE should be on by default in -current on various architectures, which is I think your primary concern. On i386 and amd64, it may well be that the performance change is not really noticeable. But increasing memory sizes on small-memory architectures is something else. With these rolled into DIAGNOSTIC, it becomes infeasible to enable the invariant-checking part of DIAGNOSTIC without these on those architectures.
So, I'd like you to still remove these from being auto-enabled, and add
them to src/sys/arch/{i386,amd64}/conf/GENERIC, and optionally on
whatever other arches make sense.
greg
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