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>
parent
adc19389
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