Hello Randy,
I tried this today but did not succeed :-( Can you please see the logs
appended below and point out what I might be doing wrong? This is on a
Red Hat 5 system.
Thanks
-Atul
+++++++++++
Sample code
+++++++++++
#include <linux/init.h>
#include <linux/version.h>
#include <linux/module.h>
MODULE_AUTHOR("LSI Corporation");
MODULE_VERSION("1.0");
MODULE_DESCRIPTION("Kernel Command Line");
MODULE_LICENSE("GPL");
static int __init cline_init(void)
{
printk("enter module:[%s]\n", saved_command_line);
return 0;
}
static void __exit cline_exit(void)
{
printk("exit module.\n");
}
module_init(cline_init);
module_exit(cline_exit);
++++++++
Makefile
++++++++
obj-m += cline.o
+++++++++
Build log
+++++++++
make: Entering directory `/usr/src/kernels/2.6.18-8.el5-i686'
LD
/usr/src/kernels/2.6.18-8.el5-i686/drivers/scsi/cline/built-in.o
CC [M] /usr/src/kernels/2.6.18-8.el5-i686/drivers/scsi/cline/cline.o
Building modules, stage 2.
MODPOST
WARNING: "saved_command_line"
[/usr/src/kernels/2.6.18-8.el5-i686/drivers/scsi/cline/cline.ko]
undefined!
CC
/usr/src/kernels/2.6.18-8.el5-i686/drivers/scsi/cline/cline.mod.o
LD [M] /usr/src/kernels/2.6.18-8.el5-i686/drivers/scsi/cline/cline.ko
make: Leaving directory `/usr/src/kernels/2.6.18-8.el5-i686'
-----Original Message-----
From: Randy Dunlap [mailto:rdunlap@xxxxxxxxxxxx]
Sent: Saturday, September 22, 2007 2:36 PM
To: Mukker, Atul
Cc: vgoyal at in.ibm.com; Moore, Eric; Kexec Mailing List
Subject: Re: kdump info request
On Fri, 21 Sep 2007 06:48:01 -0600 Mukker, Atul wrote:
> One more question, and hopefully I will not bug you further on this
:-)
>
> How exactly do you parse the kernel parameters? I thought it would be
> plain simple, but seems like the command line string is not available
to
> SCSI driver like ours, or I am missing something?
#include <linux/init.h> // for extern of 'saved_command_line' pointer.
and use calls to any functions in lib/cmdline.c or write your
own functions. Should be fairly simple to scan for a fixed string
of "elfcorehdr=".
You don't care about the variable parameters.. or do you?
> Thanks
> -Atul
>
> -----Original Message-----
> From: Vivek Goyal [mailto:vgoyal at in.ibm.com]
> Sent: Friday, September 21, 2007 12:15 AM
> To: Mukker, Atul
> Cc: Kexec Mailing List; Moore, Eric
> Subject: Re: kdump info request
>
> On Wed, Sep 19, 2007 at 07:26:19AM -0600, Mukker, Atul wrote:
> [..]
> > >
> > > If we could somehow determine that we are being called in context
of
> > capture kernel, we can dynamically lower driver memory requirement
(at
> > cost of lower IO throughout of-course, which is ok for this brief
> > context).
> >
> > You can parse the command line and look for presence of elfcorehdr=
> > option.
> > This is internally appended to command line by kexec tools to tell
> > capture
> > kernel the address of ELF core headers.
> >
> >
> > [AM] Is this a standard way? Doesn't look like one. According to
> > kernel-parameters.txt, kexec would "generally" pass this option to
> > kernel command line. Can we look at "struct resource crashk_res" and
> > check if start and end member have different value, which indicates
> > capture kernel?
> >
>
> Well, nobody else so far has had such requirements so can't say if
this
> is standard way. But this is the best way I can think of so far.
>
> Using crashk_res will not work. Not all users will use kdump and will
> not
> reserve any memory for capture kernel. In that case crashk_res will be
> zero for start and end and you don't want to trim down the
functionality
> of your driver.
>
> > What's the memory allocation requirement of current RAID driver? How
> > much
> > memory you are reserving for capture kernel? Are you already seeing
> the
> > memory allocation failure?
> >
> > [AM] Our normal runtime memory is about 20MB. For the test beds, we
> use
> > "crashkernel=192M at 16M". We have not yet seen the allocation failure
> but
> > we would like to build the fallback mechanism if it does fail under
> > capture kernel. Only if we are not able to get the normal runtime
> > memory, we plan to switch to a lower memory model.
> >
>
> 20MB is huge. I agree that it is a good idea to bring it down for
> capture
> kernel if performance is not significantly impacted.
>
> > I feel until and unless memory requirements are huge, we should not
> > compromise with IO throughput. Capability to save the dump to disk
as
> > fast
> > as possible to reduce the down time is also an important
> consideration.
> >
> > [AM] We believe our normal runtime memory requirement is
significant.
> > Also, even with the lower memory, there would not be a noticeable
dump
> > time difference since lot of memory is for supporting multiple
> > outstanding commands in driver's raid core and other raid
operations,
> > which will not be running under capture kernel. Thanks again for
your
> > feedback.
> >
>
> Makes sense.
>
> Thanks
> Vivek
>
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>
---
~Randy
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