Messages in this thread | | | Date | Tue, 10 Dec 2013 18:44:15 +0200 | From | Grygorii Strashko <> | Subject | Re: [PATCH v3 02/23] mm/memblock: debug: don't free reserved array if !ARCH_DISCARD_MEMBLOCK |
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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@ti.com> 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
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