[PATCH 3 of 6] patch: migrate to util.iterfile

Jun Wu quark at fb.com
Tue Nov 15 10:11:52 EST 2016


Excerpts from Pierre-Yves David's message of 2016-11-15 14:07:15 +0000:
> 
> On 11/15/2016 01:38 PM, Jun Wu wrote:
> > Excerpts from Yuya Nishihara's message of 2016-11-15 21:14:10 +0900:
> >> On Mon, 14 Nov 2016 23:35:55 +0000, Jun Wu wrote:
> >>> # HG changeset patch
> >>> # User Jun Wu <quark at fb.com>
> >>> # Date 1479165246 0
> >>> #      Mon Nov 14 23:14:06 2016 +0000
> >>> # Node ID d1637df5ffd91e95da25213f06f346adb3269ace
> >>> # Parent  8097b8c66952003addd5b683a14265c1d3cc201f
> >>> # Available At https://bitbucket.org/quark-zju/hg-draft 
> >>> #              hg pull https://bitbucket.org/quark-zju/hg-draft   -r d1637df5ffd9
> >>> patch: migrate to util.iterfile
> >>
> >> Not all read()s are interruptible by signals. I don't remember the detail, but
> >> signal(7) of Linux says "read(2) ... calls on "slow" devices. ... Note that a
> >> (local) disk is not a slow device according to this definition; I/O operations
> >> on disk devices are not interrupted by signals."
> >
> > Good to know! I guess modern OS have similar decisions, although POSIX seems
> > to be not helpful here.
> >
> >> Since readline() doesn't have cache in CPython layer, it would be slightly
> >> slower than fp.__iter__().
> >
> > A quick benchmark shows it's ~4x slower.
> >
> > Maybe make the function smarter to only use the workaround for a pipe?
> >
> >   if hassafeattr(fp, 'fileno') and stat.S_ISFIFO(os.fstat(fp.fileno()).st_mode):
> >       return iter(fp.readline, '')
> >   else:
> >       return fp
> 
> Should we drop this series from hg-committed or a followup is enough?

+1. I guess I have to abandon the SIGCHILD patch, too (sadly). As long as we
support Python 2.6, we are at risk that any fileobj.read() is broken.

> 
> Cheers,
> 


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