From: Nicolas Pitre <nico@cam.org>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] basic threaded delta search
Date: Thu, 06 Sep 2007 10:48:06 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.0.9999.0709061014280.21186@xanadu.home> (raw)
In-Reply-To: <7vwsv4cm6b.fsf@gitster.siamese.dyndns.org>
On Thu, 6 Sep 2007, Junio C Hamano wrote:
> Nicolas Pitre <nico@cam.org> writes:
>
> > this is still rough, hence it is disabled by default. You need to compile
> > with "make THREADED_DELTA_SEARCH=1 ..." at the moment.
> >
> > Threading is done on different portions of the object list to be
> > deltified. This is currently done by spliting the list into n parts and
> > then a thread is spawned for each of them. A better method would consist
> > of spliting the list into more smaller parts and have the n threads
> > pick the next part available.
>
> Hmmm. I wonder how the result is affected by such a partition;
> aren't you going to have many objects that could have used
> somebody else as a delta but gets stored as base because they
> happen to be a very early part of their partition (and lacking
> delta base candidates in the window)?
Yes. On a largish repo that shouldn't be significant though, not worse
than repacking multiple packs into one without -f.
> You cannot solve it with
> overlapping partitions without busting the depth limit easily
> either, I suspect.
My plan is to call find_deltas() again over partition boundaries after
adjacent partitions have been processed. If delta_child is properly
maintained in all cases (trivial) then this should just work.
> Also how would this interact with the LRU
> delta base window we discussed a week or two ago?
This is completely orthogonal.
> Separating the list into different object types would not have
> any adverse impact coming from the "horizon" of delta base
> candidates window (because we do not deltify across types), but
> that is not very useful because we cannot gain much parallerism
> from such a partition.
Indeed. Even with a straight split with equal number of objects, some
threads currently complete much faster than others. This is why a more
sophisticated distribution of work is still needed to keep the desired
amount of threads busy all the time.
Nicolas
next prev parent reply other threads:[~2007-09-06 14:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-06 6:13 [PATCH] straighten the list of objects to deltify Nicolas Pitre
2007-09-06 6:13 ` [PATCH] localize window memory usage accounting Nicolas Pitre
2007-09-06 6:13 ` [PATCH] rearrange delta search progress reporting Nicolas Pitre
2007-09-06 6:13 ` [PATCH] basic threaded delta search Nicolas Pitre
2007-09-06 6:19 ` David Kastrup
2007-09-06 6:23 ` Nicolas Pitre
2007-09-06 7:01 ` Junio C Hamano
2007-09-06 14:48 ` Nicolas Pitre [this message]
2007-09-07 6:11 ` Martin Koegler
2007-09-07 16:19 ` Nicolas Pitre
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