Hi Anton,
On 08/31/2011 09:41 AM, Anton Blanchard wrote:
>
> Hi Mahesh,
>
> Just a few comments.
>
>> +#define RMR_START 0x0
>> +#define RMR_END (0x1UL << 28) /* 256 MB */
>
> What if the RMO is bigger than 256MB? Should we be using ppc64_rma_size?
The idea was to have a minimum memory threshold that requires for a
kernel to boot successfully. On some Power systems where RMO is 128MB,
it still requires minimum of 256MB for kernel to boot successfully.
I think we can rename above #defines as BOOT_MEM_START and BOOT_MEM_END
respectively and have BOOT_MEM_END defined as below:
#define BOOT_MEM_END ((ppc64_rma_size < (0x1UL << 28)) ? \
(0x1UL << 28) : ppc64_rma_size)
What do you think?
>
>> +#ifdef DEBUG
>> +#define PREFIX "fadump: "
>> +#define DBG(fmt...) printk(KERN_ERR PREFIX fmt)
>> +#else
>> +#define DBG(fmt...)
>> +#endif
>
> We should use the standard debug macros (pr_debug etc).
Sure will do that.
>
>> +/* Global variable to hold firmware assisted dump configuration info. */
>> +static struct fw_dump fw_dump;
>
> You can remove this comment, especially because the variable isn't global :)
Agree.
>
>> + sections = of_get_flat_dt_prop(node, "ibm,configure-kernel-dump-sizes",
>> + NULL);
>> +
>> + if (!sections)
>> + return 0;
>> +
>> + for (i = 0; i < FW_DUMP_NUM_SECTIONS; i++) {
>> + switch (sections[i].dump_section) {
>> + case FADUMP_CPU_STATE_DATA:
>> + fw_dump.cpu_state_data_size =
>> sections[i].section_size;
>> + break;
>> + case FADUMP_HPTE_REGION:
>> + fw_dump.hpte_region_size =
>> sections[i].section_size;
>> + break;
>> + }
>> + }
>> + return 1;
>> +}
>
> This makes me a bit nervous. We should really get the size of the property
> and use it to iterate through the array. I saw no requirement in the PAPR
> that the array had to be 2 entries long.
>
Agree. Will make the change.
>> +static inline unsigned long calculate_reserve_size(void)
>> +{
>> + unsigned long size;
>> +
>> + /* divide by 20 to get 5% of value */
>> + size = memblock_end_of_DRAM();
>> + do_div(size, 20);
>> +
>> + /* round it down in multiples of 256 */
>> + size = size & ~0x0FFFFFFFUL;
>> +
>> + /* Truncate to memory_limit. We don't want to over reserve
>> the memory.*/
>> + if (memory_limit && size > memory_limit)
>> + size = memory_limit;
>> +
>> + return (size > RMR_END ? size : RMR_END);
>> +}
>
> 5% is pretty aribitrary, that's 400GB on an 8TB box. Also our experience
> with kdump is that 256MB is too small. Is there any reason to scale it
> with memory size? Can we do what kdump does and set it to a single
> value (eg 512MB)?
I have picked up this heuristic from the phyp-assisted dump code. I am
yet to figure out a fool-proof method to calculate the minimum memory
needed for any Power box to successfully boot. Till then, I presume we
can use this heuristic based approach?
While testing these patches on huge power system with 1TB RAM and 896
CPUs, I found that even 512MB is small. Hence setting it to a single
value may not work for all system configuration.
>
> We could override the default with a boot option, which is similar to
> how kdump specifies the region to reserve.
Agree, will work on the change.
Thanks,
-Mahesh.
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