--On Thursday, October 10, 2002 12:44:19 -0700 Andrew Morton
<[email protected]> wrote:
> Be nice to get some compelling benchmark figures onto the
> mailing lists to help push these. They're pretty late...
I've done some basic timing tests for shared page tables using a simple
fork test I wrote. It has three modes:
The first mode forks as fast as it can, then calculates how long each fork
took. This measures the time the fork() system call took.
The second mode adds a wait() for the child after the fork. The child just
calls exit(0). This measures how long the child ran.
The third mode adds an exec() in the child of a very small executable,
which just exits. This adds the exec() time to the mix.
The program also optionally allocates a shared memory object and touches
all the pages in it before the start of the test. This adds extra pages to
be dealt with by fork/exec/exit. None of the pages are touched after the
test starts.
I ran this test in three cases, 2.5.41, 2.5.41-mm2 without share, and
2.5.41-mm2 with share.
Now for the results (all times are in ms):
2.5.41 mm2-unshared mm2-shared
------ ------------ ----------
fork
----
400K 1.7 1.6 0.5
4M 5.0 5.0 3.4
40M 28.4 29.5 3.4
fork/exit
---------
400K 1.7 1.6 1.6
4M 4.9 5.3 4.1
40M 44.2 45.1 4.1
fork/exec/exit
--------------
400K 6.5 7.5 7.7
4M 10.3 11.9 10.7
40M 49.3 51.4 10.7
I don't know why exec introduces a small penalty for small tasks. I'm
working on some optimizations that might help.
Dave McCracken
======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
[email protected] T/L 678-3059
On Thu, Oct 10, 2002 at 02:59:07PM -0500, Dave McCracken wrote:
> I ran this test in three cases, 2.5.41, 2.5.41-mm2 without share, and
> 2.5.41-mm2 with share.
> Now for the results (all times are in ms):
Hrm, it'd be nice to see how nicely this does things for things like
500GB-sized processes on 64-bit boxen...
Any chance you could pass this test along for randomized benchmark
type stuff?
Thanks,
Bill
On Thu, Oct 10, 2002 at 02:59:07PM -0500, Dave McCracken wrote:
> I don't know why exec introduces a small penalty for small tasks. I'm
> working on some optimizations that might help.
Compare against vfork() to see what kind of best case is possible, and
how much of the overhead in small tasks is just in non-vm overhead.
-ben