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Re: Subversion's use of Berkeley DB [#11511]

From: Justin Erenkrantz <justin_at_erenkrantz.com>
Date: 2004-12-08 19:32:06 CET

--On Wednesday, December 8, 2004 12:15 PM -0600 "C. Michael Pilato"
<cmpilato@collab.net> wrote:

> My suggestion is that libsvn_fs_base grows the same serialization that
> mod_db4 uses, which is based around the use of a shared memory segment
> with a reference count in it. Can we make use of apr_atomics for
> something like this?

So, would we add a named shared memory segment that resides underneath the
repository - i.e. the locks subdirectory? If so, then, yes apr's shmem
routines would be able to map it in.

However, APR's atomics can't provide any guarantees outside of a single
process. If the hardware/OS supports atomics, then it does, but the APR
fallback atomic code relies upon thread mutexes. So, we'd have to use some
type of file lock as well - perhaps the db.lock we already use for recover as
well? -- justin

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Received on Wed Dec 8 19:33:59 2004

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