From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: Re: [ANNOUNCE] util-linux-ng v2.17 (stable) Date: Tue, 12 Jan 2010 15:33:26 +0200 Message-ID: <1263303206.1289.22.camel@localhost> References: <20100108093302.GS1969@nb.net.home> <4B47A713.9060405@zytor.com> <20100111140255.GA1416@ucw.cz> <4B4B5768.2040005@zytor.com> <20100111201734.GA11674@elf.ucw.cz> <4B4BB397.5090500@zytor.com> Reply-To: dedekind1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Pavel Machek , Karel Zak , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, util-linux-ng-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "H. Peter Anvin" Return-path: In-Reply-To: <4B4BB397.5090500-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org> Sender: util-linux-ng-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Mon, 2010-01-11 at 15:26 -0800, H. Peter Anvin wrote: > On 01/11/2010 12:17 PM, Pavel Machek wrote: > >> > >> Uhm, that's just plain wrong. > >> > >> It doesn't matter if there is a "special mapping layer" -- if you'= re > >> crossing multiple erase blocks you're still having more churn in > >> your flash translation layer, with more wear on the device, and > >> lower performance than if you didn't. > >=20 > > Eraseblocks really should not matter. It is not as if each logical > > sector belongs to one eraseblock.... > >=20 > > (OTOH, maybe the eraseblock *groups* that are basis for wear-leveli= ng > > do, or maybe firmware is doing something really really strange.) > > Pavel >=20 > Maybe they "should not" matter, but they *do* matter. In most existi= ng > FTLs, each logical sector *does* belong to one erase block, although > which particular erase block that is of course moves around. However= , > the invariant that matters though -- and the reason alignment matters= -- > is that for most FTLs, the *offset* of any particular logical sector > within the erase block it currently belongs to is invariant, i.e. the > FTL operates on physical sectors which are the same size as the erase > blocks. I think the other reason why alignment matters, at least on eMMC, is that they most probably have several MLC NAND chips inside, and they us= e "striping". And what matters is whether your I/O request is aligned to the "striping I/O group" size or not. Yes, because the offsets are most probably invariant. --=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) -- To unsubscribe from this list: send the line "unsubscribe util-linux-ng= " in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html