Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757980Ab2EUSdD (ORCPT ); Mon, 21 May 2012 14:33:03 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:57673 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751157Ab2EUSdA (ORCPT ); Mon, 21 May 2012 14:33:00 -0400 Date: Mon, 21 May 2012 14:32:59 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Lin Ming cc: Jens Axboe , Jeff Moyer , , , Subject: Re: [RFC v2 PATCH 2/4] block: add queue runtime pm callbacks In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1520 Lines: 38 On Mon, 21 May 2012, Lin Ming wrote: > On Mon, May 21, 2012 at 11:00 PM, Alan Stern wrote: > > On Mon, 21 May 2012, Lin Ming wrote: > > > >> On Fri, May 18, 2012 at 2:29 AM, Alan Stern wrote: > >> [snip] > >> > I may have left some parts out from this brief description. ?Hopefully > >> > you'll be able to figure out the general idea and get it to work. > >> > >> All journal threads and flusher thread of the disk need to be freezed > >> before suspend and thaw after resume. > > > > Why? ?If any of those threads needs to write something to the disk > > while the disk is suspended, the disk will simply be resumed. > > When tested the patches, I found that kjournald and flusher thread > frequently resume the disk. > > I'm not familiar with journal. > Are the journal threads still need to be in active state when the disk > is already suspended? I don't know the answers. Maybe Jens can tell us. Ideally, a rotating disk wouldn't be suspended unless all the dirty blocks were already flushed and the journal was up-to-date. For an SSD, frequently suspending and resuming doesn't matter quite so much. This may come down to a matter of setting the right value for the autosuspend timeout. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/