lkml.org 
[lkml]   [2002]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Intel P6 vs P7 system call performance


On Mon, 16 Dec 2002, dean gaudet wrote:
>
> don't many of the multi-CPU problems with tsc go away because you've got a
> per-cpu physical page for the vsyscall?

No.

The per-cpu page is _inside_ the kernel, and is only pointed at by the
SYSENTER_EIP_MSR, and not accessible from user space. It's not virtually
mapped to the same address at all.

The userspace vsyscall page is shared on the whole system, and has to be
so, because anything else is a disaster from a TLB standpoint (two threads
running on different CPU's have the same page tables, so it's basically
impossible to sanely do per-cpu TLB mappings with a hw-filled TLB like the
x86).

Linus

-
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/

\
 
 \ /
  Last update: 2005-03-22 13:31    [W:0.190 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site