Facebook hit git performance issue on large repository

Re:Facebook hit git performance issue on large repository by julian37 on Friday February 03, 2012 @06:04PM (#3549486)

Somewhat off-topic, could somebody explain why

  echo 3 | tee /proc/sys/vm/drop_caches

rather than just

  echo 3 > /proc/sys/vm/drop_caches

Is it because the output to stdout lets you be extra sure that the right data was sent to the kernel?

I'm just wondering if this is an idiom with a deeper meaning that I'm not aware of.

EDIT: I'm guessing that when you run it in a script (without set -x), rather than on the command line, you can see in the log what it is you sent?

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Re:Facebook hit git performance issue on large repository by pdw on Friday February 03, 2012 @07:14PM (#3549697)

Because you can

    echo 3 | sudo tee /proc/sys/vm/drop_caches

but

    sudo echo 3 > /proc/sys/vm/drop_caches

won't work.

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Re:Facebook hit git performance issue on large repository by julian37 on Friday February 03, 2012 @07:34PM (#3549748)

Right, that's what I was missing. That makes sense, and come to think about it, is a very useful addition to my toolbox. Thanks pdw and jochu!

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Re:Facebook hit git performance issue on large repository by tmhedberg on Saturday February 04, 2012 @11:21AM (#3551310)

You can also accomplish the same thing with:

    sudo sysctl -w vm.drop_caches=3

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Re:Facebook hit git performance issue on large repository by jochu on Friday February 03, 2012 @07:19PM (#3549708)

Aside from reasons you mentioned, I can imagine it being because it easily allows one to add a sudo or being habit because of it. For example:

  echo 3 | sudo tee /proc/sys/vm/drop_caches

Will allow you to write as root and

  sudo echo 3 > /proc/sys/vm/drop_caches

Will be a permission error. It executes the echo as root and the write as the user

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