From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH v3 0/5]add new ioctls to do metadata readahead in btrfs Date: Wed, 19 Jan 2011 18:46:36 -0800 Message-ID: <20110119184636.fed233a7.akpm@linux-foundation.org> References: <1295399715.1949.863.camel@sli10-conroe> <20110119123451.75bb3c76.akpm@linux-foundation.org> <1295490858.1949.894.camel@sli10-conroe> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Chris Mason , Christoph Hellwig , Arjan van de Ven , "Yan, Zheng" , "Wu, Fengguang" , linux-api , manpages To: Shaohua Li Return-path: In-Reply-To: <1295490858.1949.894.camel@sli10-conroe> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Thu, 20 Jan 2011 10:34:18 +0800 Shaohua Li wrote: > > > Under a harddisk based netbook with Meego, the metadata readahead > > > reduced about 3.5s boot time in average from total 16s. > > > > That's a respectable speedup. And it *needs* to be a good speedup, > > given how hacky all of this is! > > > > But then.. reducing bootup time on a laptop/desktop/server by 3.5s > > isn't exactly a world-shattering benefit, is it? Is it worth all the > > hacky code? > a laptop/desktop/server need read more data from hard disks, this will > give more bootup time saving I think, though not tested yet. Well, the whole point of the patch is to improve boot times, so the more boot-time testing you can do, the better that is! > > It would be much more valuable if those 3.5 seconds were available to > > devices which really really care about bootup times, but very few of > > those devices use rotating disks nowadays, I expect? > Currently most popular netbooks are using rotating disks actually. And > this will benefit laptop/desktop too. But my point is that three seconds boot-time improvement for a system which has an uptime of days or months isn't terribly exciting. What *would* be terribly exciting is a three-second improvement for cameras, cellphones, etc. But they don't use spinning disks. Can we expect *any* benefit for flash-type storage devices? If so, how much?