Date: Fri, 19 Aug 2016 14:27:29 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Bruce Evans <brde@optusnet.com.au> Cc: Warner Losh <imp@bsdimp.com>, Julian Elischer <julian@freebsd.org>, John Baldwin <jhb@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r304187 - in head: . share/man/man4 sys/conf sys/dev/mcd sys/modules sys/modules/mcd Message-ID: <20160819112729.GH83214@kib.kiev.ua> In-Reply-To: <20160819202010.Y2407@besplex.bde.org> References: <201608152038.u7FKc2NL026330@repo.freebsd.org> <2065331.KaGOSftJhd@ralph.baldwin.cx> <0d6c2e45-e4da-9bb7-a50c-212135d9ac4f@freebsd.org> <CANCZdfpY9S8ErwD6b7pHeH%2BRVF9JEszBb7zJ9m-wybfBr1ujAg@mail.gmail.com> <20160819073955.GC83214@kib.kiev.ua> <20160819202010.Y2407@besplex.bde.org>
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On Fri, Aug 19, 2016 at 09:12:53PM +1000, Bruce Evans wrote: > On Fri, 19 Aug 2016, Konstantin Belousov wrote: > > > On Thu, Aug 18, 2016 at 09:28:57PM -0600, Warner Losh wrote: > >> On Thu, Aug 18, 2016 at 12:50 AM, Julian Elischer <julian@freebsd.org> wrote: > >>> On 16/08/2016 4:54 AM, John Baldwin wrote: > >>>> > >>>> On Monday, August 15, 2016 08:38:02 PM John Baldwin wrote: > >>>>> ,,, > >>>>> Log: > >>>>> Remove the mcd(4) driver for Mitsumi CD-ROM players. > >>>>> This is a driver for a pre-ATAPI ISA CD-ROM adapter. As noted in > >>>>> the manpage, this driver is only useful as a backend to cdcontrol to > >>>>> play audio CDs since it doesn't use DMA, so its data performance is > >>>>> "abysmal" (and that was true in the mid 90's). > >>>> > >>>> No one stepped up to test patches for it either when I last posted patches > >>>> to > >>>> convert it from timeout(9) to callout(9). I have a few more drivers that > >>>> are > >>>> ... > >>> > >>> I would imagine any machine still holding one of these probably has not > >>> enough memory to run FreeBSD. > >>> > >>> would we still run in 2MB? > >> > >> With insane levels of tuning, we can run in 32MB userland that can do > >> things. Even 64MB is tight w/o some tuning. 16MB is almost certainly > >> right out except for very specialized situations. 2MB? We can't even > >> load the loader in that :(. Oh, and all these memory configs are only > >> possible if you tweak the loader's block cache... > > > > 32MB is quite usable. Without any tuning, you get slightly less than 10MB > > for userspace, which is enough to for many things, and plenty if swap is > > added. > > No, 32MB needs lots of needs tuning. -current seems to need about 16MB > more than just a few months ago when I last discussed this with you. > My i386 system doesn't have many drivers or a bloated userland (*), > but it took the following tuning plus my PAE tuning fixes to boot in > 32MB: > - disable [l]em1 > - reduce tx and buffers to 256 for em0. They default to 4096 for em. That > is something like 8K * 1500 bytes = 12MB for em0 alone. lem[1] wants > another 12MB. I think this is not all statically allocated, but the > drivers hang onto that much. > This now longer works. -current without my PAE tuning fixes hangs mounting > root or in usb initialization with this tuning and 40MB. -current with my > PAE tuning fixes hangs similarly with 32MB; with 40MB it boots to the > start of multiuser but then hangs (it starts 1 getty, then 2 sendmails > and kills them with "out of swap space") and 1 rpcbind (also killed). I > don't use swap, but it was needed 20 years ago on a system that actually > had 32MB of memory. > > (*) /bin/sh doing nothing much in -current i386: size 6532K res 1924K > /bin/sh in my ~5.2 i386: size 864K res 592K > > The kernel size is 5.5MB text 370K data 2.2MB bss (lots of bloat in bss > for debugging and vt). In single user mode, with 40MB to start, there > is 22116K wired and 2516K free. A few programs can be run in 2516K > without swap if they have res 592K and not 1924K. > > > Note that you cannot boot on such configurations since loader was broken, > > but if you do manage to jump to kernel, things were fine several months > > ago. I tested my relatively recent OOM changes on 32MB qemu config. > > I have no problems booting such configuratations since I don't use the > current loader and only use old loader to change the environment to > set up special configurations like this. I use my version of biosboot > for boot2. This requires fixing 2 layers of complicated breakage in > init386(). vm86 is now used before the TSS and PIC resources that it > uses are initialized, but only in paths that are not normally used > because they are for memory sizing that is normally done by loader > :-(. > > I normally use my version of biosboot for boot2. I improved its caching > just a couple of years ago. It was using 9K buffer optimized for 1440K > floppies. Now it uses a 32K buffer. Booting a 5.5MB kernel takes a > fraction of a second. Of course I don't use modules, so not many seeks > are needed. Of course I use modules and do not use GENERIC. I just tried: with today HEAD, and old loader on 32MB VM, I get 11MB free in single-user mode. Active+inactive is ~4MB, and 1M is eaten by buffers, which is about right for init+/bin/sh+top idle system. Anyway, judging from the other responses, this is the lost case.
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