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  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:	Sun, 8 Nov 2009 14:30:59 -0800
From:	Arjan van de Ven <>
To:	Corrado Zoccolo <>
	Andrew Morton <>,,,,,
	Ivan Kokshaysky <>
Subject: Re: [PATCH v2] cpuidle: Fix the menu governor to boost IO

On Sun, 8 Nov 2009 22:59:43 +0100
Corrado Zoccolo <> wrote:
> >
> > the exit latency is +/- 1 us, the entry latency is similar, and then
> > you're pretty close to 5 already (esp if you keep in mind that to
> > break even on energy you also need to be in the C state for a
> > little bit)...
> There are also performance considerations for using C1 (HLT).
> Quoting from (8-19):
> On processors supporting HT Technology, operating systems should use
> the HLT instruction if one logical processor is active and the other
> is not. HLT will allow an idle
> logical processor to transition to a halted state; this allows the
> active logical
> processor to use all the hardware resources in the physical package.

I think we all agree that long term polling is bad ;-)
(even though we use rep nop in the polling loop which is also a HT

There's just the very short sleeps (where short is "single digit usecs")
where the rules are slightly different.

> > this check is supposed to catch the known timer cases; those
> > are rather accurate in prediction
> Unfortunately, I have seen polling residency times > 1ms, so it must
> not be so accurate.

well the question is... is this a measurement error or an error in
when polling is chosen.
We obviously need to fix it whatever it is, but... first need to chase
down really which it is.

Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists