From: Abhishek Kumar <abhishekkumar8222@gmail.com>
To: git@vger.kernel.org
Cc: stolee@gmail.com, jnareb@gmail.com
Subject: [GSoC Patch v3 0/4] Move generation, graph_pos to a slab
Date: Sat, 13 Jun 2020 00:10:10 +0530 [thread overview]
Message-ID: <20200612184014.1226972-1-abhishekkumar8222@gmail.com> (raw)
The struct commit is used in many contexts. However, members
`generation` and `graph_pos` are only used for commit graph related
operations and otherwise waste memory.
This wastage would have been more pronounced as we transition to
generation number v2, which uses 64-bit generation number instead of
current 32-bits.
While the overall test suite runs slightly faster than master
(series: 27m10s, master: 27ms34s, faster by 2.35%), certain commands
like `git merge-base --is-ancestory` are slowed by nearly 40% as
discovered by SDEZER Gabor [1].
Derrick Stolee believes the slow down is attributable to the underlying
algorithm rather than the slowness of commit-slab access [2] and we will
follow-up on that in a later series.
I did not mention maximum RSS in the commit messages as they were nearly
identical (series: 68104kb, master: 68040kb, fewer by <0.1%). This leads
me to conclude that either the test using maximum memory involves commit
graph or did not involve the struct commit at all. The move to
commit-slab reduces memory footprint for the cases where struct commit
is used but members generation and graph position are not. Average RSS
would have been a good and more representative measure, but
unfortunately time(1) could not measure it on my system.
With this, I feel the patch will require minor fixes, if any. I am
moving ahead with working the next step of "Implement Generation Number
v2" that is proper handling of commit-graph format change.
Based on the discussions, I feel we should compute both generation
number v1 and the date offset value with storing date offsets in a new
chunk as the cost is mostly from walking the commits.
Abhishek Kumar (4):
alloc: introduce parsed_commits_count
commit-graph: introduce commit_graph_data_slab
commit: move members graph_pos, generation to a slab
commit-graph: minimize commit_graph_data_slab access
alloc.c | 6 +-
blame.c | 2 +-
bloom.c | 7 +-
commit-graph.c | 122 ++++++++++++++++++++++++--------
commit-graph.h | 10 +++
commit-reach.c | 69 +++++++++++-------
commit.c | 8 ++-
contrib/coccinelle/commit.cocci | 18 +++++
revision.c | 20 +++---
9 files changed, 188 insertions(+), 74 deletions(-)
--
2.27.0
Changes in v3:
- Introduce alloc commit to fix the failing diff-submodule test.
- Elaborate on performance and slow down noticed in the commit message.
Changes in v2:
- Introduce struct commit_graph_data.
- Merge `graph_pos`, `generation` slabs into a single,
`commit_graph_data` slab.
- Use graph position for an intermediate check for generation, saving
the cost of initializing generation numbers.
- Add an follow-up patch caching results of slab access in local
variables.
- Move coccinelle transformation to commit.coccinelle instead of
creating new scripts.
- Elaborate on removing default values from init_commit_node().
- Revert moving macro constants (e.g. COMMIT_NOT_FROM_GRAPH,
GENERATION_NUMBER_ZERO) from commit.h to commit-graph.h
CI Build: https://travis-ci.com/github/abhishekkumar2718/git
next reply other threads:[~2020-06-12 18:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-12 18:40 Abhishek Kumar [this message]
2020-06-12 18:40 ` [PATCH v3 1/4] alloc: introduce parsed_commits_count Abhishek Kumar
2020-06-12 20:08 ` Junio C Hamano
2020-06-12 22:00 ` Junio C Hamano
2020-06-12 22:20 ` Junio C Hamano
2020-06-12 22:52 ` Junio C Hamano
2020-06-13 18:57 ` Abhishek Kumar
2020-06-12 23:16 ` Jakub Narębski
2020-06-12 18:40 ` [PATCH v3 2/4] commit-graph: introduce commit_graph_data_slab Abhishek Kumar
2020-06-13 6:53 ` SZEDER Gábor
2020-06-17 9:18 ` Abhishek Kumar
2020-06-12 18:40 ` [PATCH v3 3/4] commit: move members graph_pos, generation to a slab Abhishek Kumar
2020-06-12 18:40 ` [PATCH v3 4/4] commit-graph: minimize commit_graph_data_slab access Abhishek Kumar
2020-06-12 21:26 ` [GSoC Patch v3 0/4] Move generation, graph_pos to a slab Jakub Narębski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200612184014.1226972-1-abhishekkumar8222@gmail.com \
--to=abhishekkumar8222@gmail.com \
--cc=git@vger.kernel.org \
--cc=jnareb@gmail.com \
--cc=stolee@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).