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Diffstat (limited to 'README/src/git/ssh-multiplex.txt')
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diff --git a/README/src/git/ssh-multiplex.txt b/README/src/git/ssh-multiplex.txt new file mode 100644 index 000000000..43f58bfb9 --- /dev/null +++ b/README/src/git/ssh-multiplex.txt @@ -0,0 +1,113 @@ +Set up SSH Mulitplexing for Speed +================================= + +This is one of my most convenient tricks. The slowest parts of `git pull` and +`git push` are starting up the SSH connection. However, there is a way to +eliminate this problem simply by opening a persistent tunnel, which `git pull` +and `git push` automatically reuse. + +~/.ssh/config +------------- + +Enter the ControlMaster option for OpenSSH. + +_________________________ +*ControlMaster* + +Enables the sharing of multiple sessions over a single network connection. +When set to “yes”, ssh(1) will listen for connections on a control socket +specified using the ControlPath argument. Additional sessions can connect to +this socket using the same *ControlPath* with *ControlMaster* set to “no” +(the default). + +These sessions will try to reuse the master instance's network connection +rather than initiating new ones, but will fall back to connecting normally if +the control socket does not exist, or is not listening. + +Setting this to “ask” will cause ssh to listen for control connections, but +require confirmation using the SSH_ASKPASS program before they are accepted +(see ssh-add(1) for details). If the *ControlPath* cannot be opened, ssh will +continue without connecting to a master instance. + +X11 and ssh-agent(1) forwarding is supported over these multiplexed +connections, however the display and agent forwarded will be the one belonging +to the master connection i.e. it is not possible to forward multiple displays +or agents. + +Two additional options allow for opportunistic multiplexing: try to use a +master connection but fall back to creating a new one if one does not already +exist. These options are: “auto” and “autoask”. The latter requires +confirmation like the “ask” option. +_________________________ + +So I set up my ~/.ssh/config as follows. + +[source,bash,numbered] +#~/.ssh/config +ControlMaster auto +ControlPath ~/.ssh/pool/%r@%h +ServerAliveCountMax 6 +ServerAliveInterval 10 +TCPKeepAlive yes + +And we're set!. + +First, a few benchmarks +----------------------- + +First, lets see how fast it is without the magic: + +[source,bash] +------ +> time for i in $( seq 0 10 ) ; do git fetch github; done + +real 0m47.798s +user 0m0.226s +sys 0m0.236s + +> time for i in $( seq 0 10 ) ; do git fetch origin; done + +real 0m48.444s +user 0m0.235s +sys 0m0.250s +------ + +Averaging about 4.34s per fetch to Github, 4.40s to gentoo overlays. + +SLOOW. + +Start a background connection +----------------------------- + +With ControlMaster, you set up a long-lived SSH connection. + +[source,bash] +------ +> ssh -fNn git@github.com +> ssh -fNn git@git.overlays.gentoo.org +------ + +And we're truely really to start cooking with petrol. + +Post Configuration Benchmarks +----------------------------- + +[source,bash] +------ +> time for i in $( seq 0 10 ) ; do git fetch github; done + +real 0m12.935s +user 0m0.093s +sys 0m0.193s + +> time for i in $( seq 0 10 ) ; do git fetch origin; done + +real 0m11.597s +user 0m0.099s +sys 0m0.191s +------ + +O_o. Averaging about 1.175s and 1.05s respectively. + + + |