From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============5142860007646666299==" MIME-Version: 1.0 From: Igor Zhbanov Subject: Re: [Powertop] Powertop doesn't detects sleeping ARM cores Date: Thu, 20 Sep 2012 14:55:43 +0400 Message-ID: <505AF62F.5070006@samsung.com> In-Reply-To: 505AF31A.4000400@linux.intel.com To: powertop@lists.01.org List-ID: --===============5142860007646666299== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Arjan van de Ven wrote: > On 9/20/2012 12:40 PM, Igor Zhbanov wrote: >> But is it correct to consider ARM core to be offline when it is just in = WFI state? > nope > > for all intents and purposes, the cpu is still there. > > in an idle state, the cpu logically is there, and ready to resume executi= on if needed... > that's the definition of idle ;-) > > offline is where the administrator takes a cpu out of circulation. > > neither specifies any physical hardware state... in fact offline is usual= ly implemented as an idle state, at > least on x86. the semantics for how to get back are different (system aut= onomous versus administrator) > > now, quite possible some ARM platforms abuse this and don't implement som= ething as "idle" but as "offline" instead. > that sounds not very smart to me. Yes, it seems that on some ARM platforms offline and idle are mixed. On my test device it is even hard to bring the core online. If I write 1 to= "online" file, then I see other pseudo-files only for a less than a second, then the core will be brought offline again. It seems that kernel powers up the core, the= n sees that there no task for it, and powers it down again. May be we should talk to ARM developers to do things more correctly. It see= ms that now impossible to administratively enable/disable some cores. The CPU governor will always= consider all available cores to be possible to use (except of limit of nr_cpus boot parameter). So I don't know what to do best. -- = Best regards, Igor Zhbanov, Expert Software Engineer, phone: +7 (495) 797 25 00 ext 3806 e-mail: i.zhbanov(a)samsung.com ASWG, Moscow R&D center, Samsung Electronics 12 Dvintsev street, building 1 127018, Moscow, Russian Federation --===============5142860007646666299==--