Re: [PATCH v4 RFT 1/2] powerpc/fadump: reduce memory consumption for capture kernel

[Hari Bathini]

On Wednesday 10 May 2017 08:28 PM, Michal Suchánek wrote:
> On Wed, 3 May 2017 12:43:33 +0530
> Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx> wrote:
>
> > On Tuesday 02 May 2017 09:26 PM, Michal Suchanek wrote:
> > > With fadump (dump capture) kernel booting like a regular kernel, it
> > > almost needs the same amount of memory to boot as the production
> > > kernel, which is unwarranted for a dump capture kernel. But with no
> > > option to disable some of the unnecessary subsystems in fadump
> > > kernel, that much memory is wasted on fadump, depriving the
> > > production kernel of that memory.
> > >
> > > Introduce kernel parameter 'fadump_append=' that would take regular
> > > kernel parameters to be appended when fadump is active.
> > > This 'fadump_append=' parameter can be leveraged to pass parameters
> > > like nr_cpus=1, cgroup_disable=memory and numa=off, to disable
> > > unwarranted resources/subsystems.
> > >
> > > Also, ensure the log "Firmware-assisted dump is active" is printed
> > > early in the boot process to put the subsequent fadump messages in
> > > context.
> > >
> > > Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > > Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
> > > ---
> > > v4:
> > >    - use space separated arguments instead of comma separated
> > >    - do not append parameters when fadummp is disabled
> > > ---
> > >    arch/powerpc/kernel/fadump.c | 27 ++++++++++++++++++++++++---
> > >    1 file changed, 24 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/fadump.c
> > > b/arch/powerpc/kernel/fadump.c index ebf2e9c..e0c728a 100644
> > > --- a/arch/powerpc/kernel/fadump.c
> > > +++ b/arch/powerpc/kernel/fadump.c
> > > @@ -79,8 +79,10 @@ int __init early_init_dt_scan_fw_dump(unsigned
> > > long node,
> > >    	 * dump data waiting for us.
> > >    	 */
> > >    	fdm_active = of_get_flat_dt_prop(node, "ibm,kernel-dump",
> > > NULL);
> > > -	if (fdm_active)
> > > +	if (fdm_active) {
> > > +		pr_info("Firmware-assisted dump is active.\n");
> > >    		fw_dump.dump_active = 1;
> > > +	}
> > >
> > >    	/* Get the sizes required to store dump data for the
> > > firmware provided
> > >    	 * dump sections.
> > > @@ -263,8 +265,12 @@ int __init fadump_reserve_mem(void)
> > >    {
> > >    	unsigned long base, size, memory_boundary;
> > >
> > > -	if (!fw_dump.fadump_enabled)
> > > +	if (!fw_dump.fadump_enabled) {
> > > +		if (fw_dump.dump_active)
> > > +			pr_warn("Firmware-assisted dump was active
> > > but kernel"
> > > +				" booted with fadump disabled!\n");
> > >    		return 0;
> > > +	}
> > >
> > >    	if (!fw_dump.fadump_supported) {
> > >    		printk(KERN_INFO "Firmware-assisted dump is not
> > > supported on" @@ -304,7 +310,6 @@ int __init
> > > fadump_reserve_mem(void) memory_boundary = memblock_end_of_DRAM();
> > >
> > >    	if (fw_dump.dump_active) {
> > > -		printk(KERN_INFO "Firmware-assisted dump is
> > > active.\n"); /*
> > >    		 * If last boot has crashed then reserve all the
> > > memory
> > >    		 * above boot_memory_size so that we don't touch
> > > it until @@ -363,6 +368,22 @@ unsigned long __init
> > > arch_reserved_kernel_pages(void) return memblock_reserved_size() /
> > > PAGE_SIZE; }
> > >
> > > +/* Look for fadump_append= cmdline option. */
> > > +static int __init early_fadump_append_param(char *p)
> > > +{
> > > +	if (!p)
> > > +		return 1;
> > > +
> > > +	if (fw_dump.fadump_enabled && fw_dump.dump_active) {
> > > +	pr_info("enforcing additional parameters (%s) passed
> > > through "
> > > +		"'fadump_append=' parameter\n", p);
> > > +		parse_early_options(p);
> > While testing this on a system with yaboot bootloader, it seems that
> > parsing a parameter with syntax like fadump_append="nr_cpus=1
> > numa=off" is not resulting in the intended way..
> Since yaboot arguments are quoted you will probably want something like
>
> append = "quiet splash somearg1 somearg2 fadump_append=\"nr_cpus=1
> numa=off\""

I did try this out. But it wasn't helping either..

> in yaboot.conf
>
> Looking at the yaboot parser it seems to handle quoting of quotes so
> unlike your parser that does not handle quoting of commas it allows
> passing arbitrary arguments to both the normal kernel and the fadump
> kernel.

Will improve on v5 to ensure quotes are taken care of..

Thanks
Hari