Subject: Re: struct msgbuf contents.
To: Matt Thomas <>
From: Simon Burge <>
List: tech-kern
Date: 06/13/2000 15:34:27
Matt Thomas wrote:

> At 01:19 PM 6/13/2000 +1000, Simon Burge wrote:
> >Locally, I've changed the members of 'struct msgbuf' from "long" to
> >"int64_t" to make 'struct msgbuf' compat32 friendly.  I've not had any
> >problems on either alpha or i386 other than the old msgbuf looking a bit
> >funny on i386 - I suspect it would fail the magic test on sparc due to
> >endianness.
> That's wrong, IMO.  If anything change them to int32_t.

I just tried int32_t and it works fine ok.  A 32 bit limit on the size
of msgbuf obviously shouldn't worry anyone...

> The overhead of
> int64 is unacceptable on many of the older platforms.

Do you have any figures for how a vax or m68k deals with say adding two
64bit numbers?

> If you are going to
> make things compat32 friendly, that's fine.  but don't make things worse
> for platforms that will never use compat32.
> Personally, I think if you are going to run 32bit programs on a 64bit
> platform, you should expect a little performance hit.

It's not performance (either way) that I'm worrying about - it's getting
the data back in a known format regardless of any differences between
the userland and kernel size.  I'm open to better/easier/quicker-natively
ways of doing this.