[GRLUG] Why aren't fast system call instructions being used on my system?

[Jeff DeFouw]

On Thu, Mar 10, 2011 at 05:20:20PM -0500, Matthew Grochowalski wrote:
> Supposedly the sysenter/sysexit instructions are significantly faster
> than the traditional 'int $0x80' method of calling a syscall. However,
> it appears 'int $0x80' is being used on my Pentium 4.
> I am not seeing 'sep' as one of the flags in /proc/cpuinfo. (sep
> indicates the process supports the sysenter/sysexit instructions).
> I am also seeing 'int $0x80' from disassembling linux-gate.dso.1

Not seeing 'sep' is the problem.  The 'sep' in /proc/cpuinfo comes from 
the same information the kernel uses to dynamically set up 
"linux-gate.dso.1".  I see it on my old Pentium III-M laptop with 2.6.26 
(Debian 686 kernel).  Something is disabling it on your system.

-- 
Jeff DeFouw <jeffd at i2k.com>

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