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Date:      Thu, 10 Jan 2019 11:00:04 +0000
From:      bugzilla-noreply@freebsd.org
To:        emulation@FreeBSD.org
Subject:   [Bug 230160] linuxulator doesn't implement madvise(MADV_DONTNEED) and any MADV_ flags with values >= 8 correctly
Message-ID:  <bug-230160-4077-0GUPjf94dr@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-230160-4077@https.bugs.freebsd.org/bugzilla/>
References:  <bug-230160-4077@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D230160

David Chisnall <theraven@FreeBSD.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|linuxulator doesn't         |linuxulator doesn't
                   |implement                   |implement
                   |madvise(MADV_DONTNEED)      |madvise(MADV_DONTNEED) and
                   |correctly                   |any MADV_ flags with values
                   |                            |>=3D 8 correctly

--- Comment #3 from David Chisnall <theraven@FreeBSD.org> ---
(In reply to Mark Johnston from comment #2)

Sorry, wanting MADV_ZERO is an unrelated issue: we have some code that would
get a very nice perf improvement if we had it.

In our own code, we implement a FreeBSD equivalent of Linux's MADV_DONTNEED=
 by
doing an mmap with MAP_FIXED over the address range.  This works fine for
anonymous memory mappings (which is all that Linux supports), but it means =
that
we have to fall back to bzero for shared memory (which means that, among ot=
her
things, we get a unique physical page for each virtual page, even though
there's a good chance that the pages are going to stay zero for a while).

--=20
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