tree 8f61c3cf73224a5c698da853b42b17579b824c0b
parent adc1938994f7f1112d335d998b5218b0aa680ad6
author Suresh Siddha <suresh.b.siddha@intel.com> 1255556815 -0700
committer H. Peter Anvin <hpa@zytor.com> 1256017560 +0900

x86-64: preserve large page mapping for 1st 2MB kernel txt with CONFIG_DEBUG_RODATA

In the first 2MB, kernel text is co-located with kernel static
page tables setup by head_64.S.  CONFIG_DEBUG_RODATA chops this
2MB large page mapping to small 4KB pages as we mark the kernel text as RO,
leaving the static page tables as RW.

With CONFIG_DEBUG_RODATA disabled, OLTP run on NHM-EP shows 1% improvement
with 2% reduction in system time and 1% improvement in iowait idle time.

To recover this, move the kernel static page tables to .data section, so that
we don't have to break the first 2MB of kernel text to small pages with
CONFIG_DEBUG_RODATA.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20091014220254.063193621@sbs-t61.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>