RE: [PATCH] intel_idle: set the state_tables array into __initdata to save mem

["Liu, Chuansheng" <chuansheng.liu@intel.com>]

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> -----Original Message-----
> From: Daniel Lezcano [mailto:daniel.lezcano@linaro.org]
> Sent: Thursday, March 07, 2013 5:49 PM
> To: Liu, Chuansheng
> Cc: lenb@kernel.org; Brown, Len; linux-pm@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] intel_idle: set the state_tables array into __initdata to
> save mem
> 
> On 03/07/2013 05:42 PM, Chuansheng Liu wrote:
> >
> > Currently, in intel_idle.c, there are 5 state_tables array, every
> > array size is sizeof(struct cpuidle_state) * CPUIDLE_STATE_MAX.
> >
> > But after intel_idle_probe(), just only one array is useful.
> >
> > Here we can just define one static state_table, and initialize it
> > in intel_idle_probe(), and set other data state_tables as __initdata.
> >
> > It can save about 3K, which also benefits mobile devices.
> >
> > Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
> > ---
> >  drivers/idle/intel_idle.c |   19 ++++++++++++-------
> >  1 files changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> > index 5d66750..0642bfe 100644
> > --- a/drivers/idle/intel_idle.c
> > +++ b/drivers/idle/intel_idle.c
> > @@ -99,7 +99,7 @@ static int intel_idle(struct cpuidle_device *dev,
> >  			struct cpuidle_driver *drv, int index);
> >  static int intel_idle_cpu_init(int cpu);
> >
> > -static struct cpuidle_state *cpuidle_state_table;
> > +static struct cpuidle_state cpuidle_state_table[CPUIDLE_STATE_MAX];
> >
> >  /*
> >   * Set this flag for states where the HW flushes the TLB for us
> > @@ -124,7 +124,7 @@ static struct cpuidle_state *cpuidle_state_table;
> >   * which is also the index into the MWAIT hint array.
> >   * Thus C0 is a dummy.
> >   */
> > -static struct cpuidle_state nehalem_cstates[CPUIDLE_STATE_MAX] = {
> > +static struct cpuidle_state nehalem_cstates[CPUIDLE_STATE_MAX]
> __initdata = {
> >  	{
> >  		.name = "C1-NHM",
> >  		.desc = "MWAIT 0x00",
> > @@ -157,7 +157,7 @@ static struct cpuidle_state
> nehalem_cstates[CPUIDLE_STATE_MAX] = {
> >  		.enter = NULL }
> >  };
> >
> > -static struct cpuidle_state snb_cstates[CPUIDLE_STATE_MAX] = {
> > +static struct cpuidle_state snb_cstates[CPUIDLE_STATE_MAX] __initdata = {
> >  	{
> >  		.name = "C1-SNB",
> >  		.desc = "MWAIT 0x00",
> > @@ -197,7 +197,7 @@ static struct cpuidle_state
> snb_cstates[CPUIDLE_STATE_MAX] = {
> >  		.enter = NULL }
> >  };
> >
> > -static struct cpuidle_state ivb_cstates[CPUIDLE_STATE_MAX] = {
> > +static struct cpuidle_state ivb_cstates[CPUIDLE_STATE_MAX] __initdata = {
> >  	{
> >  		.name = "C1-IVB",
> >  		.desc = "MWAIT 0x00",
> > @@ -237,7 +237,7 @@ static struct cpuidle_state
> ivb_cstates[CPUIDLE_STATE_MAX] = {
> >  		.enter = NULL }
> >  };
> >
> > -static struct cpuidle_state hsw_cstates[CPUIDLE_STATE_MAX] = {
> > +static struct cpuidle_state hsw_cstates[CPUIDLE_STATE_MAX] __initdata =
> {
> >  	{
> >  		.name = "C1-HSW",
> >  		.desc = "MWAIT 0x00",
> > @@ -277,7 +277,7 @@ static struct cpuidle_state
> hsw_cstates[CPUIDLE_STATE_MAX] = {
> >  		.enter = NULL }
> >  };
> >
> > -static struct cpuidle_state atom_cstates[CPUIDLE_STATE_MAX] = {
> > +static struct cpuidle_state atom_cstates[CPUIDLE_STATE_MAX] __initdata
> = {
> >  	{
> >  		.name = "C1E-ATM",
> >  		.desc = "MWAIT 0x00",
> > @@ -504,7 +504,12 @@ static int intel_idle_probe(void)
> >  	pr_debug(PREFIX "MWAIT substates: 0x%x\n", mwait_substates);
> >
> >  	icpu = (const struct idle_cpu *)id->driver_data;
> > -	cpuidle_state_table = icpu->state_table;
> > +	/* Copy the icpu->state_table into cpuidle_state_table,
> > +	 * The pointing array by icpu->state_table is with __initdata,
> > +	 * which will be freed after kernel init ending.
> > +	 */
> > +	memcpy(cpuidle_state_table, icpu->state_table,
> > +			sizeof(cpuidle_state_table));
> 
> The idea is good but it could be pushed a bit further.
> 
> Instead of changing cpuidle_state_table to an array, change it to an
> initdata and the functions intel_idle_cpuidle_driver_init,
> intel_idle_probe to init functions.
You are right. The global variable intel_idle_driver will has the copy of cpuidle_state_table[],
will update the new patch. Thanks.

> 
> That would also be nice to get rid of a global variable to store the
> current cpu data and let the intel_idle_probe to return the pointer to
> the right table.
Sounds reasonable, will have a try also. Thanks again.

> 
> 
> >  	if (boot_cpu_has(X86_FEATURE_ARAT))	/* Always Reliable APIC Timer */
> >  		lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
> >
> 
> 
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