mailing list mirror (one of many)
 help / color / mirror / code / Atom feed
From: Jeff King <>
Subject: [PATCH 0/3] index-pack threading defaults
Date: Fri, 21 Aug 2020 13:51:53 -0400	[thread overview]
Message-ID: <> (raw)

I decided to revisit index-pack's hard-coded default of 3 threads. And
it turns out that higher numbers perform much better. :)

That value was determined experimentally in 2012. I'm not sure of the
exact reason it's different now (modern processors are better at
parallelism, or modern git is better at parallelism, or the original
experiment was just a fluke). But regardless, I can get on the order of
a two-to-one speedup by bumping the thread count. See the final patch
for timings and more specific discussion.

The first two patches are just perf-test improvements (actually, the
slowness to value ratio of p5302 from the first patch is why I was
looking at this at all).

  [1/3]: p5302: disable thread-count parameter tests by default
  [2/3]: p5302: count up to online-cpus for thread tests
  [3/3]: index-pack: adjust default threading cap

 builtin/index-pack.c       | 19 ++++++++++++---
 t/perf/README              |  9 ++++++++
 t/perf/ | 47 +++++++++++++++++++-------------------
 t/perf/         |  2 ++
 4 files changed, 51 insertions(+), 26 deletions(-)


             reply	other threads:[~2020-08-21 17:51 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 17:51 Jeff King [this message]
2020-08-21 17:53 ` [PATCH 1/3] p5302: disable thread-count parameter tests by default Jeff King
2020-08-21 17:54 ` [PATCH 2/3] p5302: count up to online-cpus for thread tests Jeff King
2020-08-21 17:58   ` Jeff King
2020-08-21 17:58 ` [PATCH 3/3] index-pack: adjust default threading cap Jeff King
2020-08-21 18:08   ` Eric Sunshine
2020-08-21 18:41     ` Jeff King
2020-08-22  1:16   ` brian m. carlson
2020-08-24 17:37     ` Jeff King
2020-08-24 17:55       ` Eric Sunshine
2020-08-21 18:44 ` [PATCH 0/3] index-pack threading defaults Jeff King
2020-08-21 18:59   ` Junio C Hamano
2020-08-21 19:14     ` Jeff King

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:

  List information:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \

* 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.
Code repositories for project(s) associated with this public inbox

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 read-only IMAP folder(s) and NNTP newsgroup(s).