From: "Ludovic Courtès" <ludo@gnu.org>
To: Simon Tournier <zimon.toutoune@gmail.com>
Cc: 65787@debbugs.gnu.org
Subject: bug#65787: time-machine is doing too much network requests
Date: Sun, 10 Sep 2023 22:10:36 +0200 [thread overview]
Message-ID: <87zg1tvlfn.fsf@gnu.org> (raw)
In-Reply-To: <87wmx3mfo5.fsf@gmail.com> (Simon Tournier's message of "Wed, 06 Sep 2023 18:26:18 +0200")
Hello Simon,
This is a long message; I agree with the intent (avoiding network
traffic when the required commit is already in cache), but I’m not sure
about the analysis. It would probably be easier if you could come with
an example where there’s Git-related network traffic where there
shouldn’t.
Let me give some perspective on what the code intends to do.
‘cached-channel-instance’ has 3 cases:
1. Obvious cache hit: This is when CHANNELS specifies the commit of
each target channel (this happens for example when you type ‘guix
time-machine -q --commit=a4c35c607cfd7d6b0bad90cfcc46188d489e1754)
*and* the combination of channels is already in
~/.cache/guix/inferiors. This is the optimal case: the Git repo
doesn’t even need to be opened.
2. Cache hit: CHANNELS are pinned, but refer to tags (like “v1.2.0”)
or short commit IDs (like “a4c35c6”). In that case,
‘channel-full-commit’ opens the Git repo to resolve the identifier.
After that, we go to case #1 or #4.
3. Cache hit: CHANNELS are not pinned—i.e., they refer to a branch,
not a commit. In that case we first need to perform a ‘git fetch’
and then we go to #1 or #4.
4. Cache miss: ‘reference-available?’ returns #f for the channel
commits, we got through ‘remote-fetch’ followed by
‘build-derivations’.
As with all caches, what matters is to make sure case #1 is processes as
efficiently as possible. I believe it’s the case since the Git repo is
not even opened.
Of course it would be nice to speed up #2 and #3 too (as long as it’s
not at the expense of #1). Maybe this is the purpose of your message:
reducing Git remote accesses in those cases? (Apologies, I just
realized this might have been what you had in mind. :-))
Thanks,
Ludo’.
next prev parent reply other threads:[~2023-09-10 20:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-06 16:26 bug#65787: time-machine is doing too much network requests Simon Tournier
2023-09-10 20:10 ` Ludovic Courtès [this message]
2023-09-11 9:41 ` Simon Tournier
2023-09-11 11:36 ` Simon Tournier
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
List information: https://guix.gnu.org/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87zg1tvlfn.fsf@gnu.org \
--to=ludo@gnu.org \
--cc=65787@debbugs.gnu.org \
--cc=zimon.toutoune@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.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/guix.git
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).