[TUHS] FreeBSD behind the times? (was: Favorite unix design principles?)

[Bakul Shah]

> On Feb 5, 2021, at 6:06 PM, Dan Cross <crossd at gmail.com> wrote:
> 
> On Fri, Feb 5, 2021 at 7:04 PM Bakul Shah <bakul at iitbombay.org <mailto:bakul at iitbombay.org>> wrote:
> 
>     And you can keep track of mapped pages and read/write from them if
>     necessary even if you have a  separate cache for any compressed pages.
> 
> In essence you pass the ownership of a page's data from a compressed
> page cache to the mapped page. Just like in processor cache coherence
> algorithms there is one source of truth: the current owner of a cached
> unit (line or page or whatever). In other words, the you see via mmap(2)
> will be the exact same page you will see via read(2). Not having actually
> tried this I may have missed corner cases + any practical considerations
> complicating things but *conceptually* this doesn't seem hard.
> 
> In essence, that's what the merged page/buffer cache is all about: file IO (read/write) operations are satisfied from the same memory cache that backs up VM objects. I agree that conceptually it's not that complex; but that's not what ZFS does.

Good that we agree on that at least! This is why it would be good to hear from Bonwick/Moore.

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