Re: hammer: MAP_32BIT

H. Peter Anvin (hpa@zytor.com)
Fri, 09 May 2003 15:20:06 -0700


Timothy Miller wrote:
>
> If your program is capable of handling an address with more than 32
> bits, what point is there giving a hint? Either your program can handle
> 64-bit pointers or it cannot. Any program flexible enough to handle
> either size dynamically would expend enough overhead checking that it
> would be worse than if it just made a hard choice.
>

The purpose is that there is a slight task-switching speed advantage if
the address is in the bottom 4 GB. Since this affects every process,
and most processes use very little TLS, this is worthwhile.

This is fundamentally due to a K8 design flaw.

-hpa

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/