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Re: FSFS packing functionally complete

From: Hyrum K. Wright <hyrum_wright_at_mail.utexas.edu>
Date: Thu, 27 Nov 2008 07:33:13 -0600

Listman wrote:
> sounds like a nice feature, thx!
> just in case the performance hit is significant is there switch to
> disable this?

There isn't a switch, per se, but the filesystem is not packed by default. In
order to pack the filesystem, an administrator will need to upgrade the
repository to a modern enough format, and then run 'svnadmin pack'. Once a
repository is packed, it can't be packed. Or at least, we don't yet have a
script to do that, though I suppose it'd be possible to write one.

> On Nov 26, 2008, at 6:11 PM- Nov 26, 2008, Hyrum K. Wright wrote:
>> Hi all.
>> As of r34446, the implementation of packing on fsfs is functionally
>> complete on
>> the fsfs-pack branch. For those that don't know, packing consists of
>> mushing
>> all the individual rev files in a completed shard into one file, thus
>> eliminating the inode penalty for that entire shard. Packing a
>> trunk-generated
>> copy of the ASF repository saved about 1 GB on a 24 GB repo. There
>> may be
>> additional performance benefits in dealing with a much smaller set of
>> rev files
>> (OS caching, etc.), but I haven't yet investigated that.
>> This comes at a cost: the offsets of revisions in the pack file are
>> stored
>> separately, and thus require an additional open/seek to get that
>> information.
>> Also, determining whether a revision is stored in a pack file or not also
>> requires additional I/O. I think that most of this can be eliminated
>> with
>> caching and heuristics, but those haven't yet been implemented.
>> I'm not currently planning on including this functionality in 1.6, as
>> it's kinda
>> biggish feature, the optimizations aren't yet in place, and I feel
>> like merging
>> right before we branch 1.6.x could be a bit destabilizing. However, I
>> could
>> easily be talked into it. :)
>> Anyway, I'm soliciting feedback on the implementation and usage of
>> this feature.
>> Comments welcome.
>> -Hyrum

Received on 2008-11-27 14:33:33 CET

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