Hi Andrew, On 12/10/2013 02:11 AM, Andrew Morton wrote: > On Mon, 9 Dec 2013 16:50:35 -0500 Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote: > >> Now the Nobootmem allocator will always try to free memory allocated for >> reserved memory regions (free_low_memory_core_early()) without taking >> into to account current memblock debugging configuration >> (CONFIG_ARCH_DISCARD_MEMBLOCK and CONFIG_DEBUG_FS state). >> As result if: >> - CONFIG_DEBUG_FS defined >> - CONFIG_ARCH_DISCARD_MEMBLOCK not defined; >> - reserved memory regions array have been resized during boot >> >> then: >> - memory allocated for reserved memory regions array will be freed to >> buddy allocator; >> - debug_fs entry "sys/kernel/debug/memblock/reserved" will show garbage >> instead of state of memory reservations. like: >> 0: 0x98393bc0..0x9a393bbf >> 1: 0xff120000..0xff11ffff >> 2: 0x00000000..0xffffffff >> >> Hence, do not free memory allocated for reserved memory regions if >> defined(CONFIG_DEBUG_FS) && !defined(CONFIG_ARCH_DISCARD_MEMBLOCK). > > Alternatives: > > - disable /proc/sys/kernel/debug/memblock/reserved in this case > > - disable defined(CONFIG_DEBUG_FS) && > !defined(CONFIG_ARCH_DISCARD_MEMBLOCK) in Kconfig. Yes. But this is debug information and it's useful to have it. > > How much memory are we talking about here? If it's more than "very > little" then I think either of these would be better - most users will > value the extra memory over an accurate > /proc/sys/kernel/debug/memblock/reserved? > Sorry, I have no real statistic information and I hit this issue while testing this series by simulating huge amount of bootmem allocation during kernel boot. The real number of entries i saw on Keystone & OMAP boards is no more than ~20. Few digits below: - size of static reserved memory regions array is 2048 bytes - the size of array is doubled during each allocation Regards, -grygorii -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>