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by DblPlusUngood 2613 days ago
OpenBSD's choice is arguably reasonable, given their prioritization of security, since it reduces opportunities for user programs to corrupt kernel memory.

What is the problem with OpenBSD's plan for coherency? Why is the burden of explicitly calling msync(2) too much?
1 comments
quotemstr 2613 days ago
> reduces opportunities for user programs to corrupt kernel memory

I don't see how it could. Kernel data structures don't go on pagecache pages.

> OpenBSD's choice is arguably reasonable

At a human level, the OpenBSD people have spent way too much time coming up with rationalizations for their obsolete VM design to back down now. Whether OpenBSD's VM subsystem is good or not, their pride will force them to keep claiming that it's good, practically forever.

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DblPlusUngood 2613 days ago
> I don't see how it could. Kernel data structures don't go on pagecache pages.

Kernel data structures could end up on a pagecache page: all it takes is a reference counting bug and the page could be reallocated in the kernel heap, which is directly mapped by user space. Keeping user-mapped pages and pagecache pages distinct makes this less likely.

I am otherwise not convinced that there is an actual problem with OpenBSD's coherency plan.

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