Gentoo Archives: gentoo-user

From: Mateusz Mierzwinski <mateuszmierzwinski@××.pl>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Mounting /dev/sdaX on boot does not work
Date: Wed, 30 Jan 2008 22:17:01
In Reply to: Re: [gentoo-user] Mounting /dev/sdaX on boot does not work by Alan McKinnon
1 Alan McKinnon pisze:
2 > On Wednesday 30 January 2008, Mateusz Mierzwinski wrote:
3 >
4 >> Alan McKinnon pisze:
5 >>
6 >
7 >
8 >>> One could try listing these drivers in /etc/autoload.d/kernel-2.6
9 >>> but the easiest is probably to compile them into the kernel
10 >>>
11 >> You have right. Standard unix kernel was designed to have all inside.
12 >> I don't know why some people still prefer modules than monolith
13 >> kernel. If you have modules, you must recompile all of them when new
14 >> ABI comes out. On monolithic kernel its all there. Also i don't know
15 >> if modules are not slower than monolith Kernel because of User space
16 >> to Kernel space connection. Compiled in modules makes kernel run
17 >> faster, and if it's server, then even 0.00001 sec makes the different
18 >> on functions execution and internal core communication. Partly beyond
19 >> of that problem is IPC module communication. But if there are
20 >> benefits then also are problems with error code execution or beta
21 >> drivers installed. Also if You have Molnar's Real Time Preemption
22 >> Model on Your kernel, You should choose monolithic kernel. PS: some
23 >> drivers are don't work as modules like they should. You see Windows -
24 >> there are drivers like Linux modules - what it makes? Blue screens of
25 >> death ;), but this is another story... ;)
26 >>
27 >
28 > That's an easy answer :-)
29 >
30 > Standard Unix was designed for systems where you know exactly what
31 > hardware you have up front and there are no nasty surprises. Take for
32 > example an SGI box. How many PCI chipsets could it possibly have?
33 > Exactly one. So you know exactly which driver you will need.
34 >
35 > Apple are still lucky in this regard, as the only hardware that goes in
36 > them is Apple's hardware and kernel configurationis then quite easy.
37 >
38 > But we use the worst possible design that demented designers could ever
39 > come up with - PCs. The range of stuff available is staggering. The
40 > amount of dodgy hardware that claims to conform to spec but doesn't is
41 > even more staggering. So now exactly which modules are you going to
42 > compile in monolithically? What about hotpluggable hardware? As a
43 > vendor you have no way of knowing which funky hardware the user will
44 > ever plug into a notebook, and you simply cannot compile everything in
45 > (never mind the driver conflicts you will have).
46 >
47 > Gentoo expects their users to compile their own kernels so to a large
48 > extent we can make stuff monolithic, apart from the hot-pluggable
49 > devices.
50 >
51 > Binary distros cannot do this. To conserve memory they must load only
52 > the drivers for hardware that is actually present, and to do that one
53 > needs modules. I don;t know of a binary commercial distro that will
54 > gladly still support users who compile their own kernels - they usually
55 > stuff it all up gloriously. It's a no-brainer really.
56 >
57 > I don't buy the speedup argument either and have never seena benchmark
58 > that proves modules are slower. The Linux kernel module loader is
59 > essentially self-modifying code and inserts modules into kernel space
60 > as if they had been there monolithically (within reason of course).
61 > Some drivers do behave differently between being modular and
62 > monolithic, but this is a function of a crappy coder and not a function
63 > of modularity :-) If a piece of kernel code causes a BSOD, then it
64 > will probably do it either way it is loadable as the code is probably
65 > crappy.
66 >
67 > A Real Time kernel is not suitable for a PC either - I can't think of
68 > any RT application where a PC would be a *GOOD* choice. For that I
69 > would be using the embedded arches with a board where as designer I
70 > know exactly what is present and what isn't. Monolithic makes more
71 > sense in that case. I can imagine why Ingo made that choice - with RT
72 > he has to supply certain guarantees and probbaly can't do that with
73 > modules coming and going all the time.
74 >
75 > Basically. modern Linux is essentially unusable without kernel modules.
76 >
77 >
78 >
79 Talking about modularize kernel i think this is an gentoo mailing list
80 so every user know's his hardware - if not there is always GOOGLE,
81 Gentoo HowTo and Hardware Manual. Most drivers in kernel are universal
82 for one vendor family what makes more suitable to different types of
83 chipsets (revisions A, B etc...). There is also true that maybee kernel
84 modules are good for people with binary distro's but Gentoo is source
85 based distribution - thank god - and every user should compile kernel
86 for his hardware - modules not needed. Cheap code modules are also bad
87 rule of cheap programmers, which don't know system and kernel
88 structures. Afterwords thats how making usage of NDISWRAPPER is
89 fundamental on Windows drivers hardware.
91 If we speak about realtime preemption model i think that You are
92 mistaken saying that PC and realtime kernels (software) is not good
93 choice. My licentiate work on University of Silesia (Poland, Katowice)
94 is about usage of realtime services in computer LAN/WAN networks. I
95 digging some materials about RTOS and realtime preemption model,
96 realtime schedule algorithm and realtime applications critical points
97 programming. I don't know if PC + Realtime preemption model is something
98 wrong. When You need critical services for network such as multiplexed
99 SDH traffic control and violation prevention You must have great power
100 computer with RTOS, that can monitor min. 166MB/s traffic full duplex.
101 Now-days computers have enough power to stand with RISC (Reduced
102 Instruction Set Computing) machines - thats why Sun Solaris has arrived
103 on PC's. Another big step is RTLinux with dual core - realtime core and
104 Linux kernel working together.
106 Mateusz M.
107 --
108 gentoo-user@l.g.o mailing list


Subject Author
Re: [gentoo-user] Mounting /dev/sdaX on boot does not work Alan McKinnon <alan.mckinnon@×××××.com>