Re: fork performance

On 23/10/2012, at 10:26 AM, David Laight <[email protected]> wrote:

> On Tue, Oct 23, 2012 at 07:41:51AM +1300, Lloyd Parkes wrote:
>> I have taken 30 second ktrace from cvs 1.12.13 that shows fork
>> taking a quarter of a second every time.
>=20
> Was that before it returned in the parent, or in the child?

This is in the parent.

> I've seen issues in the past (wasn't actually NetBSD) where the child
> was scheduled before the parent (dunno which NetBSD schedules first)
> and if the child didn't block the parent's priority slowly got lower
> and lower (if the system was busy).

My test system is a VirtualBox guest with two CPUs so scheduling =
shouldn't get this pathological. The VirtualBox host has hyperthreading, =
so I can't guarantee two real CPUs though.


>> This was after cvs had been running for about 12 hours on this task =
and it
>> didn't occur to me to get a copy of its memory map before I killed =
it.
>=20
> Did you even look at the size?
> Might have been growing a lot.

I checked swap and it wasn't being used. The system had enough RAM for =
the task at hand and not much more. In fact I had to tune the vm sysctl =
stuff to avoid swapping. The system now tries to keep much more =
anonymous memory in RAM and I also reduced the target inactive =
percentage to 10% for no good reason just before the horrendous CVS =
1.12.13 test run.

Since this is VirtualBox guess, I can just fire it up again if anyone =
wants more information.

Cheers,
Lloyd