On 2020/10/6 1:12, Catalin Marinas wrote: > On Mon, Sep 07, 2020 at 09:47:43PM +0800, Chen Zhou wrote: >> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >> index 3f735cb37ace..d11d597a470d 100644 >> --- a/kernel/crash_core.c >> +++ b/kernel/crash_core.c >> @@ -378,6 +378,15 @@ int __init reserve_crashkernel_low(void) >> } >> >> #if defined(CONFIG_X86) || defined(CONFIG_ARM64) >> + >> +/* >> + * Add a threshold for required memory size of crashkernel. If required memory >> + * size is greater than threshold, just go for high allocation directly. The >> + * value of threshold is set as half of the total low memory. >> + */ >> +#define REQUIRED_MEMORY_THRESHOLD (memblock_mem_size(CRASH_ADDR_LOW_MAX >> \ >> + PAGE_SHIFT) >> 1) >> + >> #ifdef CONFIG_KEXEC_CORE >> /* >> * reserve_crashkernel() - reserves memory for crash kernel >> @@ -422,7 +431,7 @@ void __init reserve_crashkernel(void) >> * So try low memory first and fall back to high memory >> * unless "crashkernel=size[KMG],high" is specified. >> */ >> - if (!high) >> + if (!high && crash_size <= REQUIRED_MEMORY_THRESHOLD) >> crash_base = memblock_find_in_range(CRASH_ALIGN, >> CRASH_ADDR_LOW_MAX, >> crash_size, CRASH_ALIGN); > Since any change now is affecting the x86 semantics slightly, I'd > suggest you drop this patch. We can add it later if needed, once the > core changes are in. Ok, i will drop this patch in next version. Thanks, Chen Zhou > > Thinking about this, if one requires a crashkernel reservation that > allocates all of the ZONE_DMA, it would probably be noticed and explicit > ,high/,low options can be used. > > Note that we are also trying to make ZONE_DMA full 32-bit on non-RPi4 > hardware. >
