Hi all,
I'm trying to use the PyPy sandbox to execute student code on a server.
I've got it all working, but it takes a few seconds to start the sandbox
process, so the response time from the server is poor. There are a few
issues:
1) The sandbox makes a lot of system calls as part of the Python
startup. I understand how to reduce these somewhat by creating dummy
resources.
2) The sandbox invokes the C compiler to determine system
characteristics. I got a patch from Geoff Thomas as MIT (they used the
sandbox for labs in a security course). He found that this change got
rid of his C compiler invocation:
--- clean/pypy-pypy-release-1.6/pypy/rlib/rmarshal.py 2011-08-15
11:10:35.000000000 -0400
+++ pypy-pypy-release-1.6/pypy/rlib/rmarshal.py 2011-09-27
19:32:51.339470297 -0400
@@ -195,7 +195,7 @@
def dump_float(buf, x):
buf.append(TYPE_FLOAT)
- s = formatd(x, 'g', 17)
+ s = '%f' % (x)
buf.append(chr(len(s)))
buf += s
add_dumper(annmodel.SomeFloat(), dump_float)
I tried this change, and it reduced the number of compiler calls from
three to one. Before the change:
[platform:execute] gcc -c -O3 -pthread -fomit-frame-pointer -Wall
-Wno-unused /tmp/usession-default-4/platcheck_7.c -o
/tmp/usession-default-4/platcheck_7.o
Warning: cannot find your CPU L2 cache size in /proc/cpuinfo
[platform:execute] gcc -c -O3 -pthread -fomit-frame-pointer -Wall
-Wno-unused -I/home/ned/pypy/pypy/translator/c
/tmp/usession-default-4/module_cache/module_0.c -o
/tmp/usession-default-4/module_cache/module_0.o
[platform:execute] gcc -shared
/tmp/usession-default-4/module_cache/module_0.o -pthread -lrt
-Wl,--export-dynamic,--version-script=/tmp/usession-default-4/dynamic-symbols-0
-o /tmp/usession-default-4/shared_cache/externmod.so
After the change:
[platform:execute] gcc -c -O3 -pthread -fomit-frame-pointer -Wall
-Wno-unused /tmp/usession-default-3/platcheck_7.c -o
/tmp/usession-default-3/platcheck_7.o
Warning: cannot find your CPU L2 cache size in /proc/cpuinfo
I think this compile is to determine the size of floats? I don't
understand why the sandbox needs to determine this dynamically every
time it's run, and I don't understand how to get it not to, and I don't
know what bad effects the patch has. I also don't know what the
remaining compile does or how to disable it.
If someone could mentor me through this process, I would appreciate it.
Email or IRC are fine channels for me.
--Ned.
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