lkml.org 
[lkml]   [2004]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: fixmap TLB flushing clarification
>
>
>I'm curious about the last statement, is this to mean that a TLB entry will
>be reserved at set_fixmap() time in which the translation will happen, and
>that particular entry will be locked down for the duration of the mapping?
>
>
No. fixmap mappings are global - identical for all processes and all
cpus. Therefore it's not necessary to flush them during a task switch.
But that's just an optimization, not a mandatory feature:
On x86 it's possible to mark page table entries as global. Global
entries are not flushed by the normal tlb flush command, this gives a
slighly better performance. If your architecture doesn't support that,
then you can just flush everything during a task switch. I think the
support for global entries was added for the Pentium cpus - 80486 cpus
flush the whole tlb cache during a task switch.

--
Manfred



-
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 14:01    [W:0.028 / U:0.960 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site