From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: Re: New fast(?)-boot results on ARM Date: Sat, 15 Aug 2009 09:21:16 +0300 Message-ID: <4A8653DC.3050102@gmail.com> References: <20090814170228.GM13320@pengutronix.de> <4A85AAC4.7050505@acm.org> <20090814185731.GN13320@pengutronix.de> <63386a3d0908141401t6050f39ey8d85213aeccf748a@mail.gmail.com> <4A85D89F.8080900@acm.org> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4A85D89F.8080900@acm.org> Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="utf-8"; format="flowed" To: Zan Lynx Cc: Linus Walleij , Robert Schwebel , linux-kernel@vger.kernel.org, linux-embedded@vger.kernel.org, Arjan van de Ven , Tim Bird , kernel@pengutronix.de On 08/15/2009 12:35 AM, Zan Lynx wrote: > Linus Walleij wrote: >> 2009/8/14 Robert Schwebel : >>> On Fri, Aug 14, 2009 at 12:19:48PM -0600, Zan Lynx wrote: >> >>>>> That's factor 70 away from the 110 ms boot time Tim has talked ab= out >>>>> some days ago (and he measured on an ARM cpu which had almost hal= f >>>>> the speed of this one), and I'm wondering what we can do to impro= ve >>>>> the boot time. >>>> 2.4s in uncompression? That seems like an obvious target for >>>> improvement. >>> Indeed, we'll check that. >> >> We got rid of uncompression on a flash-based system vastly improving >> boot time. The reason is that compressed kernels are faster only whe= n >> the throughput to the persistent storage is lower than the decompres= sion >> throughput, and on typical embedded systems with DMA the throughput = to >> memory outperforms the CPU-based decompression. > > I thought of another thing to check related to slow decompression. If > the kernel, bootloader or hardware is in charge of setting CPU power = and > speed scaling, then you should check that it boots with the CPU set a= t > maximum speed instead of slowest. zlib is slow on decompression, and lzo is much faster. So if you implem= ent lzo compression, you'll probably speed things up a little as well. I sa= w some discussions about this on lkml. Having no compression at all may a= lso be a good thing to try. --=20 Best Regards, Artem Bityutskiy (=D0=90=D1=80=D1=82=D1=91=D0=BC =D0=91=D0=B8=D1=82=D1=8E= =D1=86=D0=BA=D0=B8=D0=B9)