Re: Can and should the kernel HZ value be changed?

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Sun, 10 Jan 1999 00:26:08 +0000


On Thu, Jan 07, 1999 at 01:13:16PM -0500, Richard B. Johnson wrote:
> On Thu, 7 Jan 1999, Chris Wedgwood wrote:
> > Oh -- and gcc sucks rocks at geenrate long long code. Not helped by
> > the fact ia32 is a horribly register starved processor.
>
> Not so. Long long stuff is as good as anyone should expect on a 32-bit
> machine. It's a lot better than 680xx stuff I've seen from compilers.

> [code example]

I've used GCC's long long stuff, and found it acceptable but not great.
I was about to write about how terrible it is, but I just tried some
tests and found the code to be quite acceptable.

There are some optimisations it's not at all good at, but on the whole
it's ok. I have written time critical code which uses long long for a
few things, where appropriate. Then again, I did tweak the compiler to
produce better code in the cases triggered by my program.

Just don't expect to divide two long longs efficiently -- the ia32
doesn't have good hardware support for that, which is why it's out of
line.

-- Jamie

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