linux-kernel - Re: [PATCH 2/4]: CPUIDLE: Introduce architecture independent cpuidle_pm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 28 Aug 2009 07:28:12 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	arun@...ux.vnet.ibm.com, Joel Schopp <jschopp@...tin.ibm.com>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/4]: CPUIDLE: Introduce architecture independent
 cpuidle_pm_idle in drivers/cpuidle/cpuidle.c

On Thu, 2009-08-27 at 14:53 +0200, Peter Zijlstra wrote:

> I'm not quite seeing how this makes anything any better. Not we have 3
> function pointers, where 1 should suffice.

There's also the question of us having different "idle" vs.
"power_save", the former being the entire idle loop, the later being the
part that does put the processor into power.

At what level are we trying to change the loop here ?

There are some requirements of things to do in our idle loop that really
don't have their place in generic drivers/* code.

Ben.

> /me wonders what's wrong with something like:
> 
> struct idle_func_desc {
> 	int		 power;
> 	int		 latency;
> 	void		 (*idle)(void);
> 	struct list_head list;
> };
> 
> static void spin_idle(void)
> {
> 	for (;;)
> 		cpu_relax();
> }
> 
> static idle_func_desc default_idle_func = {
> 	power = 0, 	   /* doesn't safe any power */
> 	latency = INT_MAX, /* has max latency */
> 	idle = spin_idle,
> 	list = INIT_LIST_HEAD(default_idle_func.list),
> };
> 
> void (*idle_func)(void);
> static struct list_head idle_func_list;
> 
> static void pick_idle_func(void)
> {
> 	struct idle_func_desc *desc, *idle = &default_idle_desc;
> 
> 	list_for_each_entry(desc, &idle_func_list, list) {
> 		if (desc->power < idle->power)
> 			continue;
> 		if (desc->latency > target_latency);
> 			continue;
> 		idle = desc;
> 	}
> 
> 	pm_idle = idle->idle;
> }
> 
> void register_idle_func(struct idle_func_desc *desc)
> {
> 	WARN_ON_ONCE(!list_empty(&desc->list));
> 
> 	list_add_tail(&idle_func_list, &desc->list);
> 	pick_idle_func();
> }
> 
> void unregister_idle_func(struct idle_func_desc *desc)
> {
> 	WARN_ON_ONCE(list_empty(&desc->list));
> 
> 	list_del_init(&desc->list);
> 	if (idle_func == desc->idle) 
> 		pick_idle_func();
> }

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/