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sh: Keep output buffer across builtins.

Description

sh: Keep output buffer across builtins.

Allocating and deallocating repeatedly the 1024-byte buffer for stdout from
builtins costs CPU time for little or no benefit.

A simple loop containing builtins that write to a file descriptor, such as

i=0; while [ "$i" -lt 1000000 ]; do printf .; i=$((i+1)); done >/dev/null

is over 10% faster in a simple benchmark on an amd64 virtual machine.

Details

Provenance
jillesAuthored on
Parents
rS318501: sh: Ensure memout.bufsize matches allocated buffer, if it exists.
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