• Richard Miller's avatar
    syscall: reduce redundant getwd tracking in Plan 9 · a379b7d9
    Richard Miller authored
    In Plan 9, each M is implemented as a separate OS process with
    its own working directory.  To keep the wd consistent across
    goroutines (or rescheduling of the same goroutine), CL 6350
    introduced a Fixwd procedure which checks using getwd and calls
    chdir if necessary before any syscall operating on a pathname.
    
    This wd checking will not be necessary if the pathname is absolute
    (starts with '/' or '#').  Getwd is a fairly expensive operation
    in Plan 9 (implemented by opening "." and calling Fd2path on the
    file descriptor).  Eliminating the redundant getwd calls can
    significantly reduce overhead for common operations like
    "dist test --list" which perform many syscalls on absolute pathnames.
    
    Updates #9428.
    
    Change-Id: I13fd9380779de27b0ac2f2b488229778d6839255
    Reviewed-on: https://go-review.googlesource.com/97675Reviewed-by: 's avatarDavid du Colombier <0intro@gmail.com>
    Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
    Run-TryBot: David du Colombier <0intro@gmail.com>
    a379b7d9
pwd_plan9.go 1.55 KB