Jun Wu <quark@fb.com> [Tue, 15 Nov 2016 20:25:51 +0000] rev 30428
util: improve iterfile so it chooses code path wisely
We have performance concerns on "iterfile" as it is 4X slower on normal
files. While modern systems have the nice property that reading a "fast"
(on-disk) file cannot be interrupted and should be made use of.
This patch dumps the related knowledge in comments. And "iterfile" chooses
code paths wisely:
1. If it's CPython 3, or PyPY, use the fast path.
2. If fp is a normal file, use the fast path.
3. If fp is not a normal file and CPython version >= 2.7.4, use the same
workaround (4x slower) as before.
4. If fp is not a normal file and CPython version < 2.7.4, use another
workaround (2x slower but may block longer then necessary) which
basically re-invents the buffer + readline logic in Python.
This will give us good confidence on both correctness and performance
dealing with EINTR in iterfile(fp) for all known supported Python versions.
Augie Fackler <augie@google.com> [Wed, 16 Nov 2016 23:29:28 -0500] rev 30427
merge with stable
Jun Wu <quark@fb.com> [Sat, 12 Nov 2016 03:06:07 +0000] rev 30426
worker: stop using a separate thread waiting for children
Now that we have a SIGCHLD hander, and it could get executed when waiting
for I/O. It's no longer necessary to have a separated waitpid thread. So
just remove it.