Looking at some of the inefficiencies in bootup (in regards to the 5
second Fedora boot), we came across MAKEDEV. To be short - it's a pig.

The only user of it in Fedora is udev, which uses it for entries in
/etc/udev/makedev.d. However, there's an already-upstream solution
of putting device nodes in /lib/udev/devices. Why not just use this,
remove MAKEDEV, simplify start_udev, and boot faster?

Bill

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On Thursday 18 September 2008 07:41:12 pm Bill Nottingham wrote:
> Looking at some of the inefficiencies in bootup (in regards to the 5
> second Fedora boot), we came across MAKEDEV. To be short - it's a pig.
>
> The only user of it in Fedora is udev, which uses it for entries in
> /etc/udev/makedev.d. However, there's an already-upstream solution
> of putting device nodes in /lib/udev/devices. Why not just use this,
> remove MAKEDEV, simplify start_udev, and boot faster?

Please

Dennis

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On Thu, 2008-09-18 at 17:41 -0700, Bill Nottingham wrote:
> The only user of it in Fedora is udev...

tpb as well.

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On Thu, Sep 18, 2008 at 09:28:34PM -0400, Ignacio Vazquez-Abrams wrote:
> > The only user of it in Fedora is udev...
> tpb as well.

It doesn't look like it would need to -- that's just in the specfile and not
in the package itself.

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> On Thursday 18 September 2008 07:41:12 pm Bill Nottingham wrote:
> > there's an already-upstream solution
> > of putting device nodes in /lib/udev/devices. Why not just use this,
> > remove MAKEDEV, simplify start_udev, and boot faster?

Please don't _remove_ MAKEDEV.
I believe the FHS requires the existence of MAKEDEV, anyway; see:
http://www.pathname.com/fhs/pub/fhs-2.3.html#DEVDEVICEFILES
There are a lot of reasons to manually create a device in /dev.

Nothing requires that the _initial_ boot use MAKEDEV, though.
If the upstream solution works and is really sound, you could use it,
and leave MAKEDEV around as a "manual override" switch.

Has this gotten enough testing, though? A post-freeze change
in fundamental boot methods might leave systems unbootable.

--- David A. Wheeler

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On Thu, Sep 18, 2008 at 10:56:45PM -0400, David A. Wheeler wrote:
> > On Thursday 18 September 2008 07:41:12 pm Bill Nottingham wrote:
> > > there's an already-upstream solution
> > > of putting device nodes in /lib/udev/devices. Why not just use this,
> > > remove MAKEDEV, simplify start_udev, and boot faster?
>
> Please don't _remove_ MAKEDEV.
> I believe the FHS requires the existence of MAKEDEV, anyway; see:
> http://www.pathname.com/fhs/pub/fhs-2.3.html#DEVDEVICEFILES
> There are a lot of reasons to manually create a device in /dev.

+1

karel

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Bill Nottingham wrote:

The only user of it in Fedora is udev, which uses it for entries in
/etc/udev/makedev.d. However, there's an already-upstream solution
of putting device nodes in /lib/udev/devices. Why not just use this,
remove MAKEDEV, simplify start_udev, and boot faster?


Another subtle source of inefficiency at boot time comes from the 64
hard-coded number virtual terminals in the kernel (tty0 to tty63).


It's particularly annoying for embedded systems because the kernel
preallocates various data structures according to this value.


The majority of udev's debug output on small systems originates from tty
initialization, although it may take very little time in practice.
Moreover, console-kit-daemon needs to create 64 threads because the
VT_WAITACTIVE ioctl is blocking as someone suggested yesterday on
#fedora-devel. It may be a big waste of resources, but it makes us look
bad in the face of Linux haters :-)


Fixing such an ancient kernel/userland interface without breaking dozens
of legaciy tools would be an interesting challenge.


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On Thu, 18 Sep 2008 17:41:12 -0700
Bill Nottingham <notting@redhat.com> wrote:

> Looking at some of the inefficiencies in bootup (in regards to the 5
> second Fedora boot), we came across MAKEDEV. To be short - it's a pig.
>
> The only user of it in Fedora is udev, which uses it for entries in
> /etc/udev/makedev.d. However, there's an already-upstream solution
> of putting device nodes in /lib/udev/devices. Why not just use this,
> remove MAKEDEV, simplify start_udev, and boot faster?

this btw can be done in two steps;
Step 1) Put the standard static device nodes in /lib/udev/devices
Step 2) Once MAKEDEV no longer is used as a result, obsolete it

Step 1) is obviously simple and can be done with no risk ... and will
in practice make MAKEDEV unused and gives you the boottime gain

Step 2) can be done later... to make people who guard freezes less
nervous


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Arjan van de Ven wrote:

On Thu, 18 Sep 2008 17:41:12 -0700
Bill Nottingham <notting@redhat.com> wrote:


Looking at some of the inefficiencies in bootup (in regards to the 5
second Fedora boot), we came across MAKEDEV. To be short - it's a pig.

The only user of it in Fedora is udev, which uses it for entries in
/etc/udev/makedev.d. However, there's an already-upstream solution
of putting device nodes in /lib/udev/devices. Why not just use this,
remove MAKEDEV, simplify start_udev, and boot faster?


this btw can be done in two steps;
Step 1) Put the standard static device nodes in /lib/udev/devices

Step 2) Once MAKEDEV no longer is used as a result, obsolete it

Step 1) is obviously simple and can be done with no risk ... and will
in practice make MAKEDEV unused and gives you the boottime gain



I switched from /lib/udev/devices to MAKEDEV!

Complaints have been filed in bugzilla, because /lib should not contain devices.
a
# grep -r foo /lib
could do harm!

selinux does not like devices in /lib also.





Step 2) can be done later... to make people who guard freezes less
nervous




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On Thu, Oct 16, 2008 at 02:42:46PM +0200, Harald Hoyer wrote:
> Arjan van de Ven wrote:
> I switched from /lib/udev/devices to MAKEDEV!
>
> Complaints have been filed in bugzilla, because /lib should not contain devices.
> a
> # grep -r foo /lib
> could do harm!
>
> selinux does not like devices in /lib also.

Why can't we put devices in /dev?

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