[PATCH 0/6 (v2)] Suggested for PU: revision caching system to significantly speed up packing/walking

* [PATCH 0/6 (v2)] Suggested for PU: revision caching system to significantly speed up packing/walking
@ 2009-08-08  7:31 Nick Edelen
  2009-08-16 22:47 ` Nick Edelen
  0 siblings, 1 reply; 5+ messages in thread
From: Nick Edelen @ 2009-08-08  7:31 UTC (permalink / raw)
  To: Junio C Hamano, Nicolas Pitre, Johannes Schindelin, Sam Vilain,
	Michael J Gruber

SUGGESTED FOR 'PU': (patchset v2)

Traversing objects is currently very costly, as every commit and tree must be 
loaded and parsed.  Much time and energy could be saved by caching metadata and 
topological info in an efficient, easily accessible manner.  Furthermore, this 
could improve git's interfacing potential, by providing a condensed summary of 
a repository's commit tree.

This is a series to implement such a revision caching mechanism, aptly named 
rev-cache.  The series will provide:
 - a core API to manipulate and traverse caches
 - an integration into the internal revision walker
 - a porcelain front-end providing access to users and (shell) applications
 - a series of tests to verify/demonstrate correctness
 - documentation of the API, porcelain and core concepts

In cold starts rev-cache has sped up packing and walking by a factor of 4, and 
over twice that on warm starts.  Some times on slax for the linux repository:

rev-list --all --objects >/dev/null
 default
   cold    1:13
   warm    0:43
 rev-cache'd
   cold    0:19
   warm    0:02

pack-objects --revs --all --stdout >/dev/null
 default
   cold    2:44
   warm    1:21
 rev-cache'd
   cold    0:44
   warm    0:10

The mechanism is minimally intrusive: most of the changes take place in 
seperate files, and only a handful of git's existing functions are modified.

Hope you find this useful.

 - Nick

---
This is a revised patchset; the biggest changes are:
 - elimination of python dependency
 - revision of documentation
 - addition of name caching (patch 6)

 Documentation/git-rev-cache.txt       |   96 ++
 Documentation/technical/rev-cache.txt |  379 ++++++
 Makefile                              |    2 +
 blob.c                                |    1 +
 blob.h                                |    2 +
 builtin-rev-cache.c                   |  309 +++++
 builtin.h                             |    1 +
 commit.c                              |    3 +
 commit.h                              |    2 +
 git.c                                 |    1 +
 list-objects.c                        |   49 +-
 rev-cache.c                           | 2041 +++++++++++++++++++++++++++++++++
 revision.c                            |   89 ++-
 revision.h                            |   47 +-
 t/t6015-rev-cache-list.sh             |  246 ++++
 tree.h                                |    1 +
 16 files changed, 3244 insertions(+), 25 deletions(-)
 create mode 100755 Documentation/git-rev-cache.txt
 create mode 100755 Documentation/technical/rev-cache.txt
 create mode 100755 builtin-rev-cache.c
 create mode 100755 rev-cache.c
 create mode 100755 t/t6015-rev-cache-list.sh

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