#10294: Slowness of pexpect interfaces on some machines
--------------------------+-------------------------------------------------
Reporter: SimonKing | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: interfaces | Keywords: pexpect select performance Ubuntu
Author: | Upstream: Reported upstream. Little or no
feedback.
Reviewer: | Merged:
Work_issues: |
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Comment(by SimonKing):
I forgot to mention a hint by Willem-Jan. He wrote on
[http://groups.google.com/group/sage-
devel/browse_thread/thread/d4b2ca2fe7ee0678 sage-devel]:
----
Could you try to download, compile and run a small test program on a
problematic machine? It times how fast a pseudo-terminal responds, which
might
be the problem judging by a few quick tests I ran.
{{{
wget http://www.usecode.org/misc/timeptmx.c
gcc -o timeptmx timeptmx.c
strace -o timeptmx.log -f -ttt ./timeptmx
grep aaa timeptmx.log
}}}
That should output something like this:
{{{
16095 1290175675.065705 write(3, "aaa", 3) = 3
16096 1290175675.065749 <... read resumed> "aaa", 256) = 3
}}}
The difference between these two timestamps seems to determine how fast
pexpect
responds. In this case it's fast (1290175675.065705 to 1290175675.065749
is
only 44 microseconds), but I've seen 1.8ms on other machines with newer
kernels.
----
I've seen even worse, namely 8ms on a Debian machine and 22ms on an Ubuntu
machine.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10294#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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