Skip Linux madvise(MADV_DONTNEED) on unmanaged objects.
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Authored by markj on Aug 17 2020, 1:06 PM.

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alc
kib

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rS364317: Skip Linux madvise(MADV_DONTNEED) on unmanaged objects.

Summary

I noticed this while reviewing the non-transparent superpages patch.
vm_object_madvise() is a no-op for unmanaged objects, but we should
limit the scope of mappings on which we'll call pmap_remove(). In
particular, with largepage objects we must remove mappings along
superpage boundaries.

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rS FreeBSD src repository - subversion

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Event Timeline

markj requested review of this revision.Aug 17 2020, 1:06 PM

markj created this revision.

Harbormaster completed remote builds in B33026: Diff 75890.Aug 17 2020, 1:06 PM

markj added reviewers: alc, kib.Aug 17 2020, 1:07 PM

I do not object, but is there a way for linux process to ever mmap largepage ?

Hmm, perhaps freebsd process can shm_open, then pass fd to linux process over unix socket, and then linux process can mmap(fd) ?

This revision is now accepted and ready to land.Aug 17 2020, 3:57 PM

alc accepted this revision.Aug 17 2020, 4:01 PM

In D26084#579065, @kib wrote:

I do not object, but is there a way for linux process to ever mmap largepage ?

Hmm, perhaps freebsd process can shm_open, then pass fd to linux process over unix socket, and then linux process can mmap(fd) ?

That's what I was thinking. Or, maybe the fd can be inherited over execve(). I am not sure if the implicit O_CLOEXEC for shm objects can be cleared.

Closed by commit rS364317: Skip Linux madvise(MADV_DONTNEED) on unmanaged objects. (authored by markj). · Explain WhyAug 17 2020, 5:15 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rS364317: Skip Linux madvise(MADV_DONTNEED) on unmanaged objects..

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