From: Johan Herland <johan@herland.net>
To: "Shawn O. Pearce" <spearce@spearce.org>
Cc: git@vger.kernel.org, gitster@pobox.com,
Johannes.Schindelin@gmx.de, trast@student.ethz.ch,
tavestbo@trolltech.com, git@drmicha.warpmail.net,
chriscool@tuxfamily.org
Subject: Re: [PATCHv5 00/14] git notes
Date: Sat, 12 Sep 2009 20:35:46 +0200 [thread overview]
Message-ID: <200909122035.47051.johan@herland.net> (raw)
In-Reply-To: <20090912181150.GN1033@spearce.org>
On Saturday 12 September 2009, Shawn O. Pearce wrote:
> Johan Herland <johan@herland.net> wrote:
> > Shawn, do you have any additional defence for the date-based fanout?
>
> No.
>
> The only defense I have for it is "it sounds like a nice theory
> given access patterns", and the note about memory usage you made,
> but which I clipped to keep this email shorter. :-)
>
> It was only a theory I tossed out there in a back-seat-driver
> sort of way. Your results show my hunch was correct, it may help.
> But they also say it may not help enough to justify the complexity,
> so I now agree with you that SHA-1 fan out may be good enough.
Ok, so I guess we can drop the flexible part of notes code. Junio: Feel free
to drop the two last patches from the jh/notes series.
> > How does the plan for notes usage in your code-review thingy
> > compare to my test scenario?
>
> I think your tests may still have been too low in volume, 115k notes
> isn't a lot. Based on the distributions I was looking at before,
> I could be seeing a growth of >100k notes/year. Ask me again in
> 5 years if 115k notes is a lot. :-)
>
> But we all know that SHA-1 distributes data quite well, so the SHA-1
> fan-out may just need to change from 2_38 to 2_2_2_34 (or something)
> to handle that larger volume.
Yes, I expect that the optimal number of entries per tree level is ~256, so
if we add an upper threshold at ~300 (where we start using another fanout
level), and a lower threshold at ~200 (where we consolidate subtrees and put
all into this level), the (still-to-be-written) writing part of the notes
code should automatically adjust the notes tree to the optimal layout.
With those assumptions, and a growth of 100k notes/year, a 2/2/36 fanout
should last you ~150 years, and a 2/2/2/34 fanout should be enough for the
next ~40,000 years... ;)
Have fun! :)
...Johan
--
Johan Herland, <johan@herland.net>
www.herland.net
next prev parent reply other threads:[~2009-09-12 18:35 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-08 2:26 [PATCHv5 00/14] git notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 01/14] Introduce commit notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 02/14] Add a script to edit/inspect notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 03/14] Speed up git notes lookup Johan Herland
2009-09-08 2:26 ` [PATCHv5 04/14] Add an expensive test for git-notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 05/14] Teach "-m <msg>" and "-F <file>" to "git notes edit" Johan Herland
2009-09-08 2:26 ` [PATCHv5 06/14] fast-import: Add support for importing commit notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 07/14] t3302-notes-index-expensive: Speed up create_repo() Johan Herland
2009-09-08 2:26 ` [PATCHv5 08/14] Add flags to get_commit_notes() to control the format of the note string Johan Herland
2009-09-08 2:26 ` [PATCHv5 09/14] Add '%N'-format for pretty-printing commit notes Johan Herland
2009-09-08 2:26 ` [PATCHv5 10/14] Teach notes code to free its internal data structures on request Johan Herland
2009-09-08 2:26 ` [PATCHv5 11/14] Teach the notes lookup code to parse notes trees with various fanout schemes Johan Herland
2009-09-08 2:27 ` [PATCHv5 12/14] Selftests verifying semantics when loading notes trees with various fanouts Johan Herland
2009-09-08 2:27 ` [PATCHv5 13/14] Allow flexible organization of notes trees, using both commit date and SHA1 Johan Herland
2009-09-08 2:27 ` [PATCHv5 14/14] Add test cases for date-based fanouts Johan Herland
2009-09-08 3:12 ` [PATCHv5 00/14] git notes Johan Herland
2009-09-08 4:16 ` Junio C Hamano
2009-09-08 8:54 ` Johan Herland
2009-09-08 9:32 ` Johannes Schindelin
2009-09-08 12:36 ` Johan Herland
2009-09-08 15:53 ` Johannes Schindelin
2009-09-08 22:46 ` Johan Herland
2009-09-10 6:23 ` Stephen R. van den Berg
2009-09-10 9:25 ` Johan Herland
2009-09-08 20:31 ` Junio C Hamano
2009-09-08 21:10 ` Shawn O. Pearce
2009-09-08 21:36 ` Sverre Rabbelier
2009-09-08 21:39 ` Shawn O. Pearce
2009-09-08 21:57 ` Sverre Rabbelier
2009-09-08 21:40 ` Johan Herland
2009-09-12 15:50 ` Johan Herland
2009-09-12 18:11 ` Shawn O. Pearce
2009-09-12 18:35 ` Johan Herland [this message]
2009-09-10 14:00 ` Geert Bosch
2009-09-10 14:09 ` Michael J Gruber
2009-09-10 14:12 ` Geert Bosch
2009-09-12 0:11 ` Junio C Hamano
2009-09-12 15:52 ` Johan Herland
2009-09-12 16:08 ` [PATCHv6 " Johan Herland
2009-09-12 16:08 ` [PATCHv6 01/14] Introduce commit notes Johan Herland
2009-09-12 16:08 ` [PATCHv6 02/14] Add a script to edit/inspect notes Johan Herland
2009-09-12 16:08 ` [PATCHv6 03/14] Speed up git notes lookup Johan Herland
2009-09-12 16:08 ` [PATCHv6 04/14] Add an expensive test for git-notes Johan Herland
2009-09-12 16:08 ` [PATCHv6 05/14] Teach "-m <msg>" and "-F <file>" to "git notes edit" Johan Herland
2009-09-12 16:08 ` [PATCHv6 06/14] fast-import: Add support for importing commit notes Johan Herland
2009-09-12 16:08 ` [PATCHv6 07/14] t3302-notes-index-expensive: Speed up create_repo() Johan Herland
2009-09-12 16:08 ` [PATCHv6 08/14] Add flags to get_commit_notes() to control the format of the note string Johan Herland
2009-09-12 16:08 ` [PATCHv6 09/14] Add '%N'-format for pretty-printing commit notes Johan Herland
2009-09-12 16:08 ` [PATCHv6 10/14] Teach notes code to free its internal data structures on request Johan Herland
2009-09-12 18:40 ` Junio C Hamano
2009-09-12 22:21 ` Johan Herland
2009-09-12 16:08 ` [PATCHv6 11/14] Teach the notes lookup code to parse notes trees with various fanout schemes Johan Herland
2009-09-12 16:08 ` [PATCHv6 12/14] Selftests verifying semantics when loading notes trees with various fanouts Johan Herland
2009-09-12 16:08 ` [PATCHv6 13/14] Allow flexible organization of notes trees, using both commit date and SHA1 Johan Herland
2009-09-12 18:41 ` Junio C Hamano
2009-09-12 22:33 ` Johan Herland
2009-09-12 23:37 ` Junio C Hamano
2009-09-12 16:08 ` [PATCHv6 14/14] Add test cases for various date-based fanouts Johan Herland
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