On Tue, May 10, 2022 at 06:55:23PM -0700, Andrew Morton wrote: > On Wed, 11 May 2022 01:05:30 +0000 Zhou Guanghui <zhouguanghui1@xxxxxxxxxx> wrote: > > > During early boot, the number of memblocks may exceed 128(some memory > > areas are not reported to the kernel due to test failures. As a result, > > contiguous memory is divided into multiple parts for reporting). If > > the size of the init memblock regions is exceeded before the array size > > can be resized, the excess memory will be lost. I'd like to see more details about how firmware creates that sparse memory map in the changelog. > > > > ... > > > > --- a/mm/Kconfig > > +++ b/mm/Kconfig > > @@ -89,6 +89,14 @@ config SPARSEMEM_VMEMMAP > > pfn_to_page and page_to_pfn operations. This is the most > > efficient option when sufficient kernel resources are available. > > > > +config MEMBLOCK_INIT_REGIONS > > + int "Number of init memblock regions" > > + range 128 1024 > > + default 128 > > + help > > + The number of init memblock regions which used to track "memory" and > > + "reserved" memblocks during early boot. > > + > > config HAVE_MEMBLOCK_PHYS_MAP > > bool > > > > diff --git a/mm/memblock.c b/mm/memblock.c > > index e4f03a6e8e56..6893d26b750e 100644 > > --- a/mm/memblock.c > > +++ b/mm/memblock.c > > @@ -22,7 +22,7 @@ > > > > #include "internal.h" > > > > -#define INIT_MEMBLOCK_REGIONS 128 > > +#define INIT_MEMBLOCK_REGIONS CONFIG_MEMBLOCK_INIT_REGIONS > > Consistent naming would be nice - MEMBLOCK_INIT versus INIT_MEMBLOCK. > > Can we simply increase INIT_MEMBLOCK_REGIONS to 1024 and avoid the > config option? It appears that the overhead from this would be 60kB or > so. 60k is not big, but using 1024 entries array for 2-4 memory banks on systems that don't report that fragmented memory map is really a waste. We can make this per platform opt-in, like INIT_MEMBLOCK_RESERVED_REGIONS ... > Or zero if CONFIG_ARCH_KEEP_MEMBLOCK and CONFIG_MEMORY_HOTPLUG > are cooperating. ... or add code that will discard unused parts of memblock arrays even if CONFIG_ARCH_KEEP_MEMBLOCK=y. -- Sincerely yours, Mike.
