Speed Up Git Pull

http://interrobeng.com/2013/08/25/speed-up-git-5x-to-50x/

by nahname • 13 years ago

146 48 13 years ago

shizcakes• 13 years ago

If you're a heavy SSH user, using multiplexing in this manner can have negative consequences [1]. Downsides include having all your multiplexed connections exiting if the master exits!

[1] http://www.anchor.com.au/blog/2010/02/ssh-controlmaster-the-...

leokun• 13 years ago

You can limit the sharing to just GithHub with a host line:

  Host github.com
  ControlMaster auto
  ControlPath /tmp/%r@%h:%p
  ControlPersist yes

dminor3• 13 years ago

Downsides include having all your multiplexed connections exiting if the master exits!

I believe this is what ControlPersist is meant to solve - it may not have existed when that blog post was written.

andrewaylett• 13 years ago

More recent SSH clients can use "ControlPersist" to establish the master connection in the background, so the first session doesn't control the lifetime of the connection. This makes using ControlMaster workable.

I usually set ControlPersist to 30 seconds, which may not be long enough for people hoping to get performance improvements from GitHub, . Setting it to too large a value increases the risk that you'll have stale server sockets after a network outage.

craigyk• 13 years ago

This makes using ControlMaster workable.

Best part of reading this article. I had turned off connection sharing because of this.

So what, in more details, are the downsides to ControlPersist?

dminor3• 13 years ago

Note that if you are on centos 6, the openssh version isn't new enough to support this feature.

er0k2• 13 years ago

this is not true

dminor3• 13 years ago

Yes it is. ControlPersist was introduced in openssh 5.6.

Centos 6 ships with a patched version of 5.3.

lsb• 13 years ago

A 50x speedup is pretty cool in its own right. Kudos.

However, I wonder if this isn't treating a symptom versus a root cause.

Is saving that 5s round-trip so common in your workflow that you needed to optimize it, and would it be more productive to refactor the app so you and collaborators are working on different files?

Also, this has the entirely valuable guidance that pushing to a local server is much faster than a remote server. There's a Github Enterprise product, for you to run close to you. It'd be an interesting calculation to see the performance hit from waiting 5s to push to a remote server, versus the performance hit from keeping your nearby server up and patched.

But nice to read, kudos all the same!

robin_reala• 13 years ago

http://xkcd.com/1205/

If you pull 10 times a day (conservative for me) then you’ll save ~5 hours over a year.

gcr2• 13 years ago

But couldn't it very well take more than 5 hours to set this up?

pugz• 13 years ago

How would refactoring help? You still need to fetch before you can push to git.

voltagex_• 13 years ago

Are there any "shorter" options for ControlPath that are still unique? I've had a few instances of silly hostnames that have caused an error about the name being too long for the socket.

nkuttler• 13 years ago

Hrm, so this isn't about making git 50x faster but fast network communication.

Establishing an SSH connection every time you perform a Git operation costs many round-trips

I don't really understand why the author is saying this. The whole point of git is to be distributed and not to push/pull at each commit.

That being said, he found something that speeds up his workflow tremendously, so congratulations.

eru3• 13 years ago

Oh, you might still want to share your commits with your coworkers, and for that you need to push and/or pull. (You could do that asynchronously, though.)

dlitz• 13 years ago

Even with a short timeout (say, 10 seconds), it could be useful for a maintainer who pulls from several other users' GitHub repositories. Instead of establishing a new SSH connection for each remote, a complete "git remote update" of multiple repositories could be done over a single connection.

CoffeeDregs• 13 years ago

Meta question: assuming that lots of GH users do this (nice trick), would GH have loads of dormant SSH connections? At scale, this could be a huge number. Would this be an issue?

ceejayoz• 13 years ago

No. I have this enabled and Github closes my connections after a very short period. I use it primarily for SSHing into my cluster of EC2 instances (which does massively speed things up).

susi22• 13 years ago

Same here. I do a

    (ssh -fqN -o "StrictHostKeyChecking no" git@bitbucket.org >&/dev/null &)

with bitbucket and github in my zshrc and bitbucket stays open but github is getting closed at some point. It used to stay open however.

scotty793• 13 years ago

...and keep your development copy of the project on ramdisk. Have a script that you launch as you start work that makes the ramsdisk and puts files from persistent location there using rsync, then periodically launches rsync to copy changes you make on our ramdisk back to persistent location.

I used this setup for almost a year. It saved me lot of time and sanity.

jlgaddis• 13 years ago

https://github.com/graysky2/anything-sync-daemon

scotty793• 13 years ago

Cool. I still prefer my 5 line bash script manually started in separate console.

gte910h2• 13 years ago

Does this buy you that much over a SSD?

scotty793• 13 years ago

Not sure. I was using it on a laptop with spinning rust for fairly large rails project.

txutxu• 13 years ago

swap on ssd is (pseudo and slower) increased ram on big needs.

Example: $5 digital ocean droplet (comes without swap, but it's over SSD, so you can create a swap file, and is less painful than mechanical swap).

dkl• 13 years ago

Too bad it doesn't work on Cygwin. (I share my ssh config between Linux and Windows.) Too bad ssh doesn't have conditional configuration. (Yes, I know I could script this, but it's a little more pain than I want for this gain.)

AceJohnny2• 13 years ago

How about VirtualBox in seamless mode instead of Cygwin?

alexchamberlain• 13 years ago

Dear GitHub,

Please setup local ssh termination to your network.

Thanks,

Alex

nilved4• 13 years ago

What can be done to prevent the "Connection to github.com closed by remote host" error that comes a few minutes after a push/pull with the Control settings enabled? Since I'm normally in vim by then, it ruins the layout.

frankil• 13 years ago

Not sure how you can stop that error, but you can run "Ctrl-L" or ":redraw" in vim to fix your layout.

verbatim• 13 years ago

Doesn't this only help if github lets you leave ssh connections open and not doing anything for long periods of time?

Surely if they do, they won't for too long if lots of people start doing this.

warmwaffles• 13 years ago

git fetch

git merge origin/master

A much preferred workflow.

hesselink• 13 years ago

I just tried the first part of this (the ssh multiplexing) and instead of getting faster, 'git fetch' got slower (1.9 to 2.4 seconds). Any ideas why, and how I can debug/improve it?

Speed Up Git Pull

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