Re: measuring shared memory on linux (was [Fwd: Re: /proc/*/statm, exactly what does "shared" mean?)]

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On Mon, 2005-02-14 at 17:39 -0500, Perrin Harkins wrote:
> > Thanks for pursuing that issue at the linux kernel list, Richard. As yo=
u=20
> > have suggested it doesn't look very good.
>=20
> I want to add my thanks too.

You are welcome.  I wish I wasn't the bearer of such bad news tho.

> Or on anything at all, since the size measurements they use include
> things that really shouldn't be counted as part of the process size.
>=20
> It seems that to tune properly you would need to send in requests with a
> benchmarking tool and keep adjusting MaxClients upward while watching
> the free memory on the box.  That's really ugly.  Maybe there's a way to
> count memory used by each process slowly but accurately which we could
> use during tuning at least.
>=20
> - Perrin

That is an ugly way, but probably the only way we have at this time.

I received further information on the linux kernel mailing list.
Basically we can apply a 'patch', okay, a *hack* that is very unlikely
to ever end up in the vanilla kernel and start maintaining it.

The way I see it, unless we patch/hack the kernel to count the
information we are interested in, we are SOL.  If we do add it, expect a
significant performance hit and don't expect it to be in the vanilla
kernel.

I am going to *try* and take the code sample I was given and wedge it
into the right place on a machine sometime this week.  If it works, I'll
let you know.  Maybe we can convince someone on lkml that if we make a
way to turn this *feature* on or off with a sysctl and put it somewhere
else in /proc/<pid/* that they'll put it in the vanilla kernel.  Then
someone with more of a clue than I have can maintain it :)

Best,

Richard


--=20
Richard F. Rebel

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