From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: Abhishek Kumar <abhishekkumar8222@gmail.com>,
git@vger.kernel.org, jnareb@gmail.com
Subject: Re: [GSoC Patch 0/3] Move generation, graph_pos to a slab
Date: Sun, 7 Jun 2020 21:53:47 +0200 [thread overview]
Message-ID: <20200607195347.GA8232@szeder.dev> (raw)
In-Reply-To: <b850637d-a7ca-e8f9-5009-657096ea2975@gmail.com>
On Thu, Jun 04, 2020 at 10:22:27AM -0400, Derrick Stolee wrote:
> On 6/4/2020 3:27 AM, Abhishek Kumar wrote:
> > 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 transistion to
> > generation number v2, which uses 64-bit generation number instead of
> > current 32-bits.
>
> Thanks! This is an important step, and will already improve
> performance in subtle ways.
While the reduced memory footprint of each commit object might improve
performance, accessing graph position and generation numbers in a
commit-slab is more expensive than direct field accesses in 'struct
commit' instances. Consequently, these patches increase the runtime
of 'git merge-base --is-ancestor HEAD~50000 HEAD' in the linux
repository from 0.630s to 0.940s.
> > create mode 100644 contrib/coccinelle/generation.cocci
> > create mode 100644 contrib/coccinelle/graph_pos.cocci
>
> I appreciate the Coccinelle scripts to help identify
> automatic fixes for other topics in-flight. However,
> I wonder if they would be better placed inside the
> existing commit.cocci file?
We add Coccinelle scripts to avoid undesirable code patterns entering
our code base. That, however, is not the case here: this is a
one-time conversion, and at the end of this series 'struct commit'
won't have a 'generation' field anymore, so once it's merged the
compiler will catch any new 'commit->generation' accesses. Therefore
I don't think that these Coccinelle scripts should be added at all.
next prev parent reply other threads:[~2020-06-07 19:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 7:27 [GSoC Patch 0/3] Move generation, graph_pos to a slab Abhishek Kumar
2020-06-04 7:27 ` [GSoC Patch 1/3] commit: introduce helpers for generation slab Abhishek Kumar
2020-06-04 14:36 ` Derrick Stolee
2020-06-04 17:35 ` Junio C Hamano
2020-06-05 23:23 ` Jakub Narębski
2020-06-04 7:27 ` [GSoC Patch 2/3] commit: convert commit->generation to a slab Abhishek Kumar
2020-06-04 14:27 ` Derrick Stolee
2020-06-04 17:49 ` Junio C Hamano
2020-06-06 22:03 ` Jakub Narębski
2020-06-04 7:27 ` [GSoC Patch 3/3] commit: convert commit->graph_pos " Abhishek Kumar
2020-06-07 12:12 ` Jakub Narębski
2020-06-04 14:22 ` [GSoC Patch 0/3] Move generation, graph_pos " Derrick Stolee
2020-06-04 17:55 ` Junio C Hamano
2020-06-07 19:53 ` SZEDER Gábor [this message]
2020-06-08 5:48 ` Abhishek Kumar
2020-06-08 8:36 ` SZEDER Gábor
2020-06-08 13:45 ` Derrick Stolee
2020-06-08 16:46 ` SZEDER Gábor
2020-06-08 15:21 ` Jakub Narębski
2020-06-05 19:00 ` Jakub Narębski
2020-06-07 19:32 ` [GSOC Patch v2 0/4] " Abhishek Kumar
2020-06-07 19:32 ` [GSOC Patch v2 1/4] commit-graph: introduce commit_graph_data_slab Abhishek Kumar
2020-06-15 16:27 ` Taylor Blau
2020-06-07 19:32 ` [GSOC Patch v2 2/4] commit: move members graph_pos, generation to a slab Abhishek Kumar
2020-06-08 8:26 ` SZEDER Gábor
2020-06-08 12:35 ` Derrick Stolee
2020-06-07 19:32 ` [GSOC Patch v2 3/4] commit-graph: use generation directly when writing commit-graph Abhishek Kumar
2020-06-08 16:31 ` Jakub Narębski
2020-06-15 16:31 ` Taylor Blau
2020-06-07 19:32 ` [GSOC Patch v2 4/4] commit-graph: minimize commit_graph_data_slab access Abhishek Kumar
2020-06-08 16:22 ` [GSOC Patch v2 0/4] Move generation, graph_pos to a slab Jakub Narębski
2020-06-15 16:24 ` Taylor Blau
2020-06-17 9:14 ` [GSOC Patch v4 " Abhishek Kumar
2020-06-17 9:14 ` [GSOC Patch v4 1/4] object: drop parsed_object_pool->commit_count Abhishek Kumar
2020-06-17 9:14 ` [GSOC Patch v4 2/4] commit-graph: introduce commit_graph_data_slab Abhishek Kumar
2020-06-17 9:14 ` [GSOC Patch v4 3/4] commit: move members graph_pos, generation to a slab Abhishek Kumar
2020-06-17 9:14 ` [GSOC Patch v4 4/4] commit-graph: minimize commit_graph_data_slab access Abhishek Kumar
2020-06-19 13:59 ` [GSOC Patch v4 0/4] Move generation, graph_pos to a slab Derrick Stolee
2020-06-19 17:44 ` Junio C Hamano
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