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[PATCH] powerpc: Fix runlatch performance issues

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The runlatch SPR can take a lot of time to write. My original runlatch
code would set it on every exception entry even though most of the time
this was not required. It would also continually set it in the idle
loop, which is an issue on an SMT capable processor.

Now we cache the runlatch value in a threadinfo bit, and only check for
it in decrementer and hardware interrupt exceptions as well as the idle
loop. Boot on POWER3, POWER5 and iseries, and compile tested on pmac32.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Anton Blanchard
2006-02-13 14:48:35 +11:00
committed by Paul Mackerras
parent 47f78a4920
commit cb2c9b2741
5 changed files with 39 additions and 41 deletions
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32
arch/powerpc/kernel/process.c
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@@ -888,3 +888,35 @@ void dump_stack(void)
show_stack(current, NULL);
}
EXPORT_SYMBOL(dump_stack);
#ifdef CONFIG_PPC64
void ppc64_runlatch_on(void)
{
unsigned long ctrl;
if (cpu_has_feature(CPU_FTR_CTRL) && !test_thread_flag(TIF_RUNLATCH)) {
HMT_medium();
ctrl = mfspr(SPRN_CTRLF);
ctrl |= CTRL_RUNLATCH;
mtspr(SPRN_CTRLT, ctrl);
set_thread_flag(TIF_RUNLATCH);
}
}
void ppc64_runlatch_off(void)
{
unsigned long ctrl;
if (cpu_has_feature(CPU_FTR_CTRL) && test_thread_flag(TIF_RUNLATCH)) {
HMT_medium();
clear_thread_flag(TIF_RUNLATCH);
ctrl = mfspr(SPRN_CTRLF);
ctrl &= ~CTRL_RUNLATCH;
mtspr(SPRN_CTRLT, ctrl);
}
}
#endif