From: Colby Ranger <cranger@google.com>
To: Jeff King <peff@peff.net>
Cc: "Shawn Pearce" <spearce@spearce.org>,
"Vicent Martí" <tanoku@gmail.com>, git <git@vger.kernel.org>
Subject: Re: [PATCH 09/16] documentation: add documentation for the bitmap format
Date: Wed, 26 Jun 2013 11:41:12 -0700 [thread overview]
Message-ID: <CAFFbUKJZ1w2puKFLjPNZmMhSLo3_1kpfA1upv7K6qZV256vTyQ@mail.gmail.com> (raw)
In-Reply-To: <20130626051117.GB26755@sigill.intra.peff.net>
> Pinning the bitmap index on the reverse index adds complexity (lookups
> are two-step: first find the entry in the reverse index, and then find
> the SHA1 in the index) and is measurably slower, in both loading and
> lookup times. Since Git doesn't have a memory problem, it's very hard
> to make an argument for design that is more complex and runs slower to
> save memory.
Sorting by SHA1 will generate a random distribution. This will require
you to inflate the entire bitmap on every fetch request, in order to
do the "contains" operation. Sorting by pack offset allows us to
inflate only the bits we need as we are walking the graph, since they
are usually at the start of the bitmap.
What is the general size in bytes of the SHA1 sorted bitmaps? If they
are much larger, the size of the bitmap has an impact on how fast you
can perform bitwise operations on them, which is important for fetch
when doing wants AND NOT haves.
next prev parent reply other threads:[~2013-06-26 18:41 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-24 23:22 [PATCH 00/16] Speed up Counting Objects with bitmap data Vicent Marti
2013-06-24 23:22 ` [PATCH 01/16] list-objects: mark tree as unparsed when we free its buffer Vicent Marti
2013-06-24 23:22 ` [PATCH 02/16] sha1_file: refactor into `find_pack_object_pos` Vicent Marti
2013-06-25 13:59 ` Thomas Rast
2013-06-24 23:23 ` [PATCH 03/16] pack-objects: use a faster hash table Vicent Marti
2013-06-25 14:03 ` Thomas Rast
2013-06-26 2:14 ` Jeff King
2013-06-26 4:47 ` Jeff King
2013-06-25 17:58 ` Ramkumar Ramachandra
2013-06-25 22:48 ` Junio C Hamano
2013-06-25 23:09 ` Vicent Martí
2013-06-24 23:23 ` [PATCH 04/16] pack-objects: make `pack_name_hash` global Vicent Marti
2013-06-24 23:23 ` [PATCH 05/16] revision: allow setting custom limiter function Vicent Marti
2013-06-24 23:23 ` [PATCH 06/16] sha1_file: export `git_open_noatime` Vicent Marti
2013-06-24 23:23 ` [PATCH 07/16] compat: add endinanness helpers Vicent Marti
2013-06-25 13:08 ` Peter Krefting
2013-06-25 13:25 ` Vicent Martí
2013-06-27 5:56 ` Peter Krefting
2013-06-24 23:23 ` [PATCH 08/16] ewah: compressed bitmap implementation Vicent Marti
2013-06-25 1:10 ` Junio C Hamano
2013-06-25 22:51 ` Junio C Hamano
2013-06-25 15:38 ` Thomas Rast
2013-06-24 23:23 ` [PATCH 09/16] documentation: add documentation for the bitmap format Vicent Marti
2013-06-25 5:42 ` Shawn Pearce
2013-06-25 19:33 ` Vicent Martí
2013-06-25 21:17 ` Junio C Hamano
2013-06-25 22:08 ` Vicent Martí
2013-06-27 1:11 ` Shawn Pearce
2013-06-27 2:36 ` Vicent Martí
2013-06-27 2:45 ` Jeff King
2013-06-27 16:07 ` Shawn Pearce
2013-06-27 17:17 ` Jeff King
2013-07-01 18:47 ` Colby Ranger
2013-07-01 19:13 ` Shawn Pearce
2013-07-07 9:46 ` Jeff King
2013-07-07 17:27 ` Shawn Pearce
2013-06-26 5:11 ` Jeff King
2013-06-26 18:41 ` Colby Ranger [this message]
2013-06-26 22:33 ` Colby Ranger
2013-06-27 0:53 ` Colby Ranger
2013-06-27 1:32 ` Shawn Pearce
2013-06-27 1:29 ` Shawn Pearce
2013-06-25 15:58 ` Thomas Rast
2013-06-25 22:30 ` Vicent Martí
2013-06-26 23:12 ` Thomas Rast
2013-06-26 23:19 ` Thomas Rast
2013-06-24 23:23 ` [PATCH 10/16] pack-objects: use bitmaps when packing objects Vicent Marti
2013-06-25 12:48 ` Ramkumar Ramachandra
2013-06-25 15:58 ` Thomas Rast
2013-06-25 23:06 ` Junio C Hamano
2013-06-25 23:14 ` Vicent Martí
2013-06-24 23:23 ` [PATCH 11/16] rev-list: add bitmap mode to speed up lists Vicent Marti
2013-06-25 16:22 ` Thomas Rast
2013-06-26 1:45 ` Vicent Martí
2013-06-26 23:13 ` Thomas Rast
2013-06-26 5:22 ` Jeff King
2013-06-24 23:23 ` [PATCH 12/16] pack-objects: implement bitmap writing Vicent Marti
2013-06-24 23:23 ` [PATCH 13/16] repack: consider bitmaps when performing repacks Vicent Marti
2013-06-25 23:00 ` Junio C Hamano
2013-06-25 23:16 ` Vicent Martí
2013-06-24 23:23 ` [PATCH 14/16] sha1_file: implement `nth_packed_object_info` Vicent Marti
2013-06-24 23:23 ` [PATCH 15/16] write-bitmap: implement new git command to write bitmaps Vicent Marti
2013-06-24 23:23 ` [PATCH 16/16] rev-list: Optimize --count using bitmaps too Vicent Marti
2013-06-25 16:05 ` [PATCH 00/16] Speed up Counting Objects with bitmap data Thomas Rast
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