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[PATCH] fast vdso implementation for CLOCK_THREAD_CPUTIME_ID

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The extract cpu time instruction (ectg) instruction allows the user
process to get the current thread cputime without calling into the
kernel. The code that uses the instruction needs to switch to the
access registers mode to get access to the per-cpu info page that
contains the two base values that are needed to calculate the current
cputime from the CPU timer with the ectg instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2008-12-31 15:11:42 +01:00
parent 9cfb9b3c3a
commit c742b31c03
10 changed files with 222 additions and 32 deletions
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9
arch/s390/kernel/smp.c
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@ -47,6 +47,7 @@
#include <asm/lowcore.h>
#include <asm/sclp.h>
#include <asm/cpu.h>
#include <asm/vdso.h>
#include "entry.h"
/*
@ -506,6 +507,9 @@ static int __cpuinit smp_alloc_lowcore(int cpu)
goto out;
lowcore->extended_save_area_addr = (u32) save_area;
}
#else
if (vdso_alloc_per_cpu(cpu, lowcore))
goto out;
#endif
lowcore_ptr[cpu] = lowcore;
return 0;
@ -528,6 +532,8 @@ static void smp_free_lowcore(int cpu)
#ifndef CONFIG_64BIT
if (MACHINE_HAS_IEEE)
free_page((unsigned long) lowcore->extended_save_area_addr);
#else
vdso_free_per_cpu(cpu, lowcore);
#endif
free_page(lowcore->panic_stack - PAGE_SIZE);
free_pages(lowcore->async_stack - ASYNC_SIZE, ASYNC_ORDER);
@ -670,6 +676,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
lowcore = (void *) __get_free_pages(GFP_KERNEL | GFP_DMA, lc_order);
panic_stack = __get_free_page(GFP_KERNEL);
async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
BUG_ON(!lowcore || !panic_stack || !async_stack);
#ifndef CONFIG_64BIT
if (MACHINE_HAS_IEEE)
save_area = get_zeroed_page(GFP_KERNEL);
@ -683,6 +690,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
#ifndef CONFIG_64BIT
if (MACHINE_HAS_IEEE)
lowcore->extended_save_area_addr = (u32) save_area;
#else
BUG_ON(vdso_alloc_per_cpu(smp_processor_id(), lowcore));
#endif
set_prefix((u32)(unsigned long) lowcore);
local_mcck_enable();