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Re: Using LMDB safely with fork() and exec()

On 24. aug. 2016 11:02, Lorenz Bauer wrote:

On 24 August 2016 at 06:27, Hallvard Breien Furuseth
<h.b.furuseth@usit.uio.no <mailto:h.b.furuseth@usit.uio.no>> wrote:
    The unix version only uses O_DIRECT if psize >= OS psize
    because O_DIRECT typically requires alignment on OS page
    boundaries, or something like that.  Should be commented.
    Didn't find anything similar in the Windows doc, but again,
    I don't know Windows.  Maybe Howard knows more.

According to man 2 open O_DIRECT alignment is file system specific from 2.6
onwards, but "usually" 512bytes FWIW. Not sure how that would affect this code.


I gather you mean Linux 2.6.  But O_DIRECT is not Linux-specific, I
don't know of a portable way to ask "is this alignment big enough?",
and the code breaks if we use O_DIRECT when the OS doesn't like it.
So we simply assume the OS page size is OK.

--
Hallvard