ntdb for Samba 4.2?

Rusty Russell rusty at samba.org
Wed Mar 19 23:03:01 MDT 2014

Volker Lendecke <Volker.Lendecke at SerNet.DE> writes:
> On Wed, Mar 19, 2014 at 02:48:33PM +1030, Rusty Russell wrote:
>> Meanwhile, there's no demand to drive it.  TDB has problems, but scaling
>> over 3GB isn't the main one.  The locking speed has been greatly
>> improved by the addition of inline mutexes; and so you won't notice
>> freelist contention as much.  And using dbwrap means the new API doesn't
>> even make the code cleaner.
> Even with mutexes you do notice freelist contention. The
> real kick for this in our tests is the patch from
> yesterday: With TDB_VOLATILE we keep some dead records per
> chain, and while the freelist is blocked we go fishing for
> dead records in other chains. Essentially, this turns each
> chain into a small freelist. This together with mutexes
> really, really rocks. No futex syscalls around anymore even
> for heavily loaded servers. :-)

Yes, this is a really good idea.  I'd love to see a benchmark
included in tdb which demonstrated the improvement, too.  I'm
not sure tdbtorture will do it.

        5f7b481349796cc0e90563ed01353809b403e429 tdb: Fix a tdb corruption

I don't understand how this can corrupt?  A test case should be fairly
simple, but I think this change is unnecessary.

The rest of the patches look really nice.  By changing to first fit you
may increase fragmentation, but since TDBs are already so fragmented I
don't think it'll be measurable.


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