Date: Tue, 8 May 2007 11:45:12 +0800 From: "Mars G. Miro" <marsgmiro@gmail.com> To: freebsd-stable@freebsd.org, "Oliver Fromme" <olli@lurza.secnetix.de> Subject: Re: mfs and buildworlds on the SunFire x4600 Message-ID: <28edec3c0705072045s18a2cb53ia4f66030e4e3fb22@mail.gmail.com> In-Reply-To: <200705072228.l47MSCSr048972@lurza.secnetix.de> References: <28edec3c0705071447t64eb6ea1n7a18550d4af6d883@mail.gmail.com> <200705072228.l47MSCSr048972@lurza.secnetix.de>
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On 5/8/07, Oliver Fromme <olli@lurza.secnetix.de> wrote: > Mars G. Miro wrote: > > Oliver Fromme wrote: > > > By the way, what are you actually trying to do? What is > > > your goal? Do you need to reduce the buildworld time? > > > > as i've mentioned in my original email, does mfs speed up I/O stuff ? > > Sometimes it does. But most of the time, a real disk > partition with soft-updates on it is just as fast. > With soft-updates, writing is asynchronous, i.e. it > goes to RAM first, just like a memory disk. The data > is later committed to disk in the background, so the > processes don't have to wait for it. And once the > data is in the cache, reading is just as fast (or even > faster) as a memory disk. Note that /usr/src will > fit in the cache easily if you have several GB of RAM. > > I usually have a memory disk as /tmp, but that's really > just for historical reasons. And it's easier to clean > up -- just umount it. ;-) > > > there's been a lot of threads in teh past that a buildworld on mfs > > increases speed --- tho it might not be the appropriate test for > > high-end machines (speaking of w/c I just gots a T2000). > > It depends on what exactly you want to test, and for > what reason. You probably have already wasted much > more time with your experiments and testing than you > can ever save by using mfs for buildworld. > wasted my time? dont think so. now we know buildworld on mfs dont really matter on high-end machines, and it didnt even then when i tried it on my single-proc Opteron w/ 1G of RAM almost 2 years ago on 5.X (i recall having to crash when i used malloc but then this is documented) and I'd think testing it on something like my x4100 w/ 8G of RAM may produce the same results.. so teh conclusion would be, buildworld isnt teh appropriate test if mfs does really speed things up, other apps/tools may be much more appropriate --- that or, does mfs speeding things up really work? remains to be seen ... > > there's prolly other appropriate apps/tools for mfs-testing ... > > I don't think it makes much sense to benchmark mfs. > It is a known fact that a real tmpfs (like Solaris and > Linux have) would be better. I think it's even listed > on the FreeBSD ideas web page, but nobody is actively > working on it, AFAIK. On the other hand, I'm not 100% > convinced that it would be worth the effort either. > it does to me, however, and perhaps other people too ;-) > It would be interesting to see how ZFS on a swap-backed > vnode device would perform on FreeBSD 7-current (with > and without compression). > > Best regards > Oliver > > -- > Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. > Handelsregister: Registergericht Muenchen, HRA 74606, Gesch=E4ftsfuehrun= g: > secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht M=FC= n- > chen, HRB 125758, Gesch=E4ftsf=FChrer: Maik Bachmann, Olaf Erb, Ralf Geb= hart > > FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd > > One Unix to rule them all, One Resolver to find them, > One IP to bring them all and in the zone to bind them. > cheers mars
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