fix(cmd): Use buffered reads#389
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Popen defaults to using unbuffered reads, which are extremely slow.
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Byron commented Feb 25, 2016
Thanks for bringing this up ! Even though I might have had the hunch that parsing git command output is a bit slow, it never struck me as being due to disabled buffering - apparently I wanted to believe it's just due to python. |
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Popen in many versions of Python (possibly all versions prior to 3.3.1?) defaults to using unbuffered reads (bufsize=0), which are extremely slow. When reading a 160k-line file from git, unbuffered reads take 5.75s; buffered reads take 0.23s.
Newer versions of Python 3 appear to change the default to bufsize=-1 so this may only be a problem for a subset of users, but it certainly was a problem for me. I’m not sure of any reason not to just use buffered reads by default for everyone, so I am submitting this patch for evaluation. Thanks!