Hello Pingfan,
Thanks for the patch..
On 19/02/20 7:48 PM, Pingfan Liu wrote:
> 'mem=" option is an easy way to put high pressure on memory during some
> test. Hence after applying the memory limit, instead of total mem, the
> actual usable memory should be considered when reserving mem for
> crashkernel. Otherwise the boot up may experience OOM issue.
>
> E.g. it would reserve 4G prior to the change and 512M afterward, if passing
> crashkernel="2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G", and
> mem=5G on a 256G machine.
>
> This issue is powerpc specific because it puts higher priority on fadump
> and kdump reservation than on "mem=". Referring the following code:
> if (fadump_reserve_mem() == 0)
> reserve_crashkernel();
> ...
> /* Ensure that total memory size is page-aligned. */
> limit = ALIGN(memory_limit ?: memblock_phys_mem_size(), PAGE_SIZE);
> memblock_enforce_memory_limit(limit);
>
> While on other arches, the effect of "mem=" takes a higher priority and pass
> through memblock_phys_mem_size() before calling reserve_crashkernel().
>
> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> To: linuxppc-dev@xxxxxxxxxxxxxxxx
> Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: kexec@xxxxxxxxxxxxxxxxxxx
> ---
> v2 -> v3: improve commit log
> arch/powerpc/kernel/machine_kexec.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> index c4ed328..eec96dc 100644
> --- a/arch/powerpc/kernel/machine_kexec.c
> +++ b/arch/powerpc/kernel/machine_kexec.c
> @@ -114,11 +114,12 @@ void machine_kexec(struct kimage *image)
>
> void __init reserve_crashkernel(void)
> {
> - unsigned long long crash_size, crash_base;
> + unsigned long long crash_size, crash_base, total_mem_sz;
> int ret;
>
> + total_mem_sz = memory_limit ? memory_limit : memblock_phys_mem_size();
> /* use common parsing */
> - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> + ret = parse_crashkernel(boot_command_line, total_mem_sz,
> &crash_size, &crash_base);
> if (ret == 0 && crash_size > 0) {
> crashk_res.start = crash_base;
memory_limit is adjusted after this with the below snippet:
/* Crash kernel trumps memory limit */
if (memory_limit && memory_limit <= crashk_res.end) {
memory_limit = crashk_res.end + 1;
printk("Adjusted memory limit for crashkernel, now 0x%llx\n",
memory_limit);
}
So, either the above snippet must be dropped or the print below should use an updated total_mem_sz
based on adjusted memory_limit. I would prefer the latter..
> @@ -185,7 +186,7 @@ void __init reserve_crashkernel(void)
> "for crashkernel (System RAM: %ldMB)\n",
> (unsigned long)(crash_size >> 20),
> (unsigned long)(crashk_res.start >> 20),
> - (unsigned long)(memblock_phys_mem_size() >> 20));
> + (unsigned long)(total_mem_sz >> 20));
>
> if (!memblock_is_region_memory(crashk_res.start, crash_size) ||
> memblock_reserve(crashk_res.start, crash_size)) {
>
--
- Hari
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