From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 06/10] libata: implement new Power Management framework Date: Tue, 13 Jun 2006 11:08:07 +0900 Message-ID: <448E1E07.7010803@gmail.com> References: <11501274293403-git-send-email-htejun@gmail.com> <1150130098.25462.10.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from py-out-1112.google.com ([64.233.166.181]:55001 "EHLO py-out-1112.google.com") by vger.kernel.org with ESMTP id S932775AbWFMCIP (ORCPT ); Mon, 12 Jun 2006 22:08:15 -0400 Received: by py-out-1112.google.com with SMTP id x31so1859256pye for ; Mon, 12 Jun 2006 19:08:14 -0700 (PDT) In-Reply-To: <1150130098.25462.10.camel@localhost.localdomain> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: jgarzik@pobox.com, lkml@rtr.ca, axboe@suse.de, forrest.zhao@intel.com, linux-ide@vger.kernel.org Alan Cox wrote: > Ar Maw, 2006-06-13 am 00:50 +0900, ysgrifennodd Tejun Heo: >> Suspend is performed parallely on all ports of a host_set and resume >> is done parallely in background to decrease the time necessary before >> responding to user. > > Do we need a disk count here - some large disk setups rely on the fact > drives don't all spin up at once to avoid overloading the PSU ? For most desktops and notebooks, it doesn't really matter as power is removed from disks during memsleep and they all spin up immediately after resume regardless of what libata does. For external enclosures with separate power supply, limiting the number of concurrent spinups during resume is necessary though. I think we need to make a central disk spinup limiter to control the number of concurrent spinups across both ATA and SCSI. SATA staggered spinup should be considered too. Depending on situation, a drive may spin up on power up, PHY ready or IDLE_IMM after resuming from memsleep. FWIW, my cheapo 325w PSU (< 30USD) hasn't had any problem spinning up 11 drives simultaneously. I think it's okay to leave it as it is for the time being. It's not like people w/ external enclosures use suspend/resume a lot. -- tejun