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

[Pierre-Yves David]

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?

Cheers,

-- 
Pierre-Yves David