Date: Fri, 5 Dec 2014 13:12:29 +0000 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: FreeBSD working from RAM (MFSROOT) as a Workstation. Message-ID: <20141205131229.5ebd96d2@gumby.homeunix.com> In-Reply-To: <447fy665uf.fsf@be-well.ilk.org> References: <1417734458.1772.1.camel@zoho.com> <447fy665uf.fsf@be-well.ilk.org>
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On Fri, 05 Dec 2014 00:08:56 -0500 Lowell Gilbert wrote: > clutton <clutton@zoho.com> writes: > > > Is anyone use a FreeBSD as a Desktop working from RAM, using > > MFSROOT? > > That only speeds up the *first* load of each memory page mirroring a > disk sector. After the system has been up a while, it's actually > slower than running with a disk, because everything you actually use > will have two copies in RAM: one on the disk image, and the one > that's actually occupying normal resident pages. I don't know much about MFSROOT, but I doubt that's right. It seems unlikely that the kernel caches ram in ram, the normal expectation is that a single copy of a page is used until it needs to be copied-on-write. > TL;DR: To run from RAM, you first have to load the RAM. The chances > that an MFSROOT does this more efficiently (than starting directly > from the nonvolatile disk) seem remote. It depends on what you care about. If you aren't bothered by the time it takes to boot, on a desktop it may be preferable take a lot of separate reads off the critical path. An alternative might be to do a conventional boot and then kick-off a background script that pre-caches as much of the SSD as will fit in the remaining free memory. I'd try this first because it's a lot less trouble and will give a reasonable indication of how much thing can be speeded-up (at least until the cache is driven-out by something else).
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