Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 25 May 2023 10:13:39 -0700 | Subject | Re: Extending page pinning into fs/direct-io.c |
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On Thu, May 25, 2023 at 10:01 AM David Howells <dhowells@redhat.com> wrote: > > What do we gain from it? Presumably since nothing is supposed to write to > that page, it can be shared in all the caches.
I don't remember the details, but they went something like "broken purely virtually indexed cache avoids physical aliases by cacheline exclusion at fill time".
Which then meant that if you walk a zero mapping, you'll invalidate the caches of the previous page when you walk the next one. Causing horrendously bad performance.
Unless it's colored.
Something like that. I probably got all the details wrong.
Linus
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