Re: [Tracker] Update for qdbm

[Philip Van Hoof <spam pvanhoof be>]

On Fri, 2008-07-25 at 09:04 -0400, Jamie McCracken wrote:
> > With this patch you can update qdbm in src/qdbm for all branches and
> > TRUNK.
> >
> > We are not planning to do this just yet, but I had done it for some
> > tests anyway, and perhaps in near future it might be useful?
 
> that patch removes all my optimizations that I applied to qdbm!
>
> IE use of fdatasync instead of fsync and readahead optimisations

Are these optimizations secured against two processes each having their
own depot instance, but a shared mmap()?

I can imagine the fsync() stuff being involved with getting this right.

Because I noticed that, in tracker's depot.c, depot->bucket[x] = y is
only ever done during dpput(), which is a function that is never called
by a consumer of the depot file that only ever reads.

With two threads that's fine because the same memory for depot and
depot->bucket is used.

ïThe content of ïdepot->bucket[x] is read by dpget() to see if there's
something in the bucket. In my tests the content of each and every
bucket is always 0 for a reading process, but filled up for a writing
process (if they are different processes).

With two processes there are two allocations for each. Thus I don't see
how this can work with two processes then :-\

Anyway, we plan to on-flush let the indexer tell trackerd to unload the
depot file at the next read.

> also adds all the crap that we dont use (my version just included the
> minimal source we needed)


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