I have been looking thru the kernel code trying to understand how the ker=
nel
memory allocation works etc. and have noticed a few things.=20

When the autoconfig routine installs a device driver it mallocs some memo=
ry
for the softc device structure and this is passed to the driver to use. =20

see: sys/kern/subr_autoconf.c  config_attach()

The malloc routine allocates memory from kernel space, I am not sure if t=
his
memory is wired down or not.  I have noticed that some device drivers use=
 this
memory for buffers (the 16550 com.c driver com_intr()  )  while others us=
e the
bus_dma functions ( ethernet etc.) to guarantee they have wired down memo=
ry.

Is the softc driver memory wired down? or will it page?  It seems to me i=
t
should be wired down and should not page.  If they page should the autoco=
nf
routine force the memory to be wired down?  This may improve the performa=
nce of=20
device drivers.

Also shouldnt the ISR routines be wired down so they do not page?  My
understanding is that kernel code can be paged in and out.

Thanks in advance
--=20
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Mark Milligan
Real Time Systems Inc.