On Fri, Aug 19, 2016 at 3:35 AM, Toomas Soome <tso...@me.com> wrote: > >> On 19. aug 2016, at 12:24, Konstantin Belousov <kostik...@gmail.com> wrote: >> >> On Fri, Aug 19, 2016 at 11:50:35AM +0300, Toomas Soome wrote: >>> >>>> On 19. aug 2016, at 10:39, Konstantin Belousov <kostik...@gmail.com> 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 <jul...@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: >>>>>>>> >>>>>>>> Author: jhb >>>>>>>> Date: Mon Aug 15 20:38:02 2016 >>>>>>>> New Revision: 304187 >>>>>>>> URL: https://svnweb.freebsd.org/changeset/base/304187 >>>>>>>> >>>>>>>> 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 >>>>>>> both very old and that people have no business using in 12 (think ISA >>>>>>> adapters that don't do DMA and can't be used with pccard) that I will be >>>>>>> removing over the next little while. I brought up a list of drivers on >>>>>>> arch@ >>>>>>> a couple of years ago and the conversation drifted off into the weeds >>>>>>> about >>>>>>> trimming GENERIC, etc. No one objected to the specific drivers I listed >>>>>>> though (and I got a few pleas of "please remove"). If someone shows up >>>>>>> desperately clutching an ISA adapter they can always dig up the source >>>>>>> from >>>>>>> svn and deal with forward porting it for whatever API changes have >>>>>>> happened >>>>>>> since it was removed. >>>>>> >>>>>> >>>>>> 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. >>>> >>>> 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. >>>>> Warner >>>> >>> >>> If the target is to go as low memory as possible, sure, you can strip all >>> off, from boot loader point, you should load kernel from stage2 and not use >>> loader at all (you can load and jump kernel even now from stage2, assuming >>> it wont need any special configuration from loader config) etc etc. This >>> means highly specialized build and has nothing to do with generic all >>> purpose system. >>> >> Why you describe this as an 'alternative' ? Before that loader changes, >> I regularly tested on 32MB qemy i386 image and 64MB amd64 image. I do >> not see anything extreme in these configs. They use normal boot path, >> which provides kernels with debugging symbols, metadata, loaded modules >> etc. Why should I use deficient boot2-only loading, which, additionally, >> cannot work on amd64 ? >> >> More, this is the only reasonable way for most developers to ensure that >> system is still usable on tiny configs found on embedded devices. Right >> now the min which I have to set up is 128MB, and VM changes are simply not >> tested on anything smaller. It is guaranteed that small systems will grow >> regressions fast. And I will not jump through the hoops to mitigate >> breakage induced by other people' changes. >> >>> Also at some point, there is an question about how reasonable it is to have >>> such configuration as part of generic code base for special bits like boot >>> loader itself, as the problem is, testing all those variants is becoming >>> impossible and even keeping reasonable code base in all of the #if #else >>> #endif spaghetti is getting quite hard and error prone. >>> >>>> From developers point of view, it is not really encouraging to have >>>> possible feedback like ???oh, but you did break my 32MB system boot??? ;) >>>> This does bring back some memories however. For first 2 unix systems I was >>>> dealing with, one had 8MB and another had 12MB of memory??? it was ~ >>>> 1992-1993;) >>> >> Not mine, but you (?) indirectly broke system for people who do use 32MB >> on other arches, since low memory config on dev systems become 128MB. >> I cared about 32MB before, but not any longer. > > > Yep, I did set it to 64MB. And this is exactly why I wrote that small systems > do need special approaches, because getting updates for new features and > keeping tiny systems functional are conflicting options. So far freebsd boot > loader has managed this in some extent by massive amount of preprocessor > conditions and the result is insane list of different boot programs in
There's only one boot program that's bloated recently, and that's /boot/loader. the static allocation of large buffers because malloc isn't working well is the problem. This isn't a small system vs large system problem, but a convenience vs complexity problem. Installing the base boot loader (that loads /boot/loader or kernel) is and always will be system dependent with very real constraints. Warner _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
