linux-kernel - Re: [PATCH 2/2] x86/idle: use dynamic halt poll

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]

Message-ID: <e6a78334-c9c1-0b0b-9d62-f6ade04cf93f@gmail.com>
Date:   Fri, 23 Jun 2017 12:04:40 +0800
From:   Yang Zhang <yang.zhang.wz@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     mingo@...hat.com, hpa@...or.com, pbonzini@...hat.com,
        x86@...nel.org, corbet@....net, tony.luck@...el.com, bp@...en8.de,
        peterz@...radead.org, mchehab@...nel.org,
        akpm@...ux-foundation.org, krzk@...nel.org, jpoimboe@...hat.com,
        luto@...nel.org, borntraeger@...ibm.com, thgarnie@...gle.com,
        rgerst@...il.com, minipli@...glemail.com,
        douly.fnst@...fujitsu.com, nicstange@...il.com, fweisbec@...il.com,
        dvlasenk@...hat.com, bristot@...hat.com,
        yamada.masahiro@...ionext.com, mika.westerberg@...ux.intel.com,
        yu.c.chen@...el.com, aaron.lu@...el.com, rostedt@...dmis.org,
        me@...ehuey.com, len.brown@...el.com, prarit@...hat.com,
        hidehiro.kawai.ez@...achi.com, fengtiantian@...wei.com,
        pmladek@...e.com, jeyu@...hat.com, Larry.Finger@...inger.net,
        zijun_hu@....com, luisbg@....samsung.com, johannes.berg@...el.com,
        niklas.soderlund+renesas@...natech.se, zlpnobody@...il.com,
        adobriyan@...il.com, fgao@...ai8.com, ebiederm@...ssion.com,
        subashab@...eaurora.org, arnd@...db.de, matt@...eblueprint.co.uk,
        mgorman@...hsingularity.net, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-edac@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/idle: use dynamic halt poll

On 2017/6/22 22:32, Thomas Gleixner wrote:
> On Thu, 22 Jun 2017, root wrote:
>> @@ -962,6 +962,7 @@ __visible void __irq_entry smp_apic_timer_interrupt(struct pt_regs *regs)
>>  	 * interrupt lock, which is the WrongThing (tm) to do.
>>  	 */
>>  	entering_ack_irq();
>> +	check_poll();
>
> No way, that we sprinkle this function into every interrupt hotpath. There
> are enough genuine ways to do that w/o touching a gazillion of files.

I will find a more correct place to call this function.

>
>>  #ifdef CONFIG_HYPERVISOR_GUEST
>> +static unsigned int grow_poll_ns(unsigned int old, unsigned int grow,
>> +				      unsigned int max)
>> +{
>> +	unsigned int val;
>> +
>> +	/* 10us as base poll duration */
>> +	if (old == 0 && grow)
>> +		return 10000;
>> +
>> +	val = old * grow;
>> +	if (val > max)
>> +		val = max;
>> +
>> +	return val;
>> +}
>> +
>> +static unsigned int shrink_poll_ns(unsigned int old, unsigned int shrink)
>> +{
>> +	if (shrink == 0)
>> +		return 0;
>> +
>> +	return old / shrink;
>> +}
>> +
>> +void check_poll(void)
>> +{
>> +	unsigned int val, poll_duration;
>> +	unsigned long begin_ns, now_ns;
>> +
>> +	if (!poll_threshold_ns)
>> +		return;
>
> If at all then this needs to be a static key based decision.

Sure, will do it.

>
>> +
>> +	begin_ns = this_cpu_read(poll_begin_ns);
>> +	/* Not from halt state */
>> +	if (!begin_ns)
>> +		return;
>
> If you integrate this stuff into the proper place, then the whole mess goes
> away. We really do not need another facility to track idle state. We have
> enough already, really.

Agree, I will check current code to find a more proper way to do the check.

>
> Thanks,
>
> 	tglx
>


-- 
Yang
Alibaba Cloud Computing