Messages in this thread | | | Date | Wed, 04 Sep 2013 10:05:51 +0800 | From | Tang Chen <> | Subject | Re: [PATCH 07/11] x86, memblock: Set lowest limit for memblock_alloc_base_nid(). |
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On 09/04/2013 08:37 AM, Toshi Kani wrote: > On Tue, 2013-08-27 at 17:37 +0800, Tang Chen wrote: >> memblock_alloc_base_nid() is a common API of memblock. And it calls >> memblock_find_in_range_node() with %start = 0, which means it has no >> limit for the lowest address by default. >> >> memblock_find_in_range_node(0, max_addr, size, align, nid); >> >> Since we introduced current_limit_low to memblock, if we have no limit >> for the lowest address or we are not sure, we should pass >> MEMBLOCK_ALLOC_ACCESSIBLE to %start so that it will be limited by the >> default low limit. >> >> dma_contiguous_reserve() and setup_log_buf() will eventually call >> memblock_alloc_base_nid() to allocate memory. So if the allocation order >> is from low to high, they will allocate memory from the lowest limit >> to higher memory. > > This requires the callers to use MEMBLOCK_ALLOC_ACCESSIBLE instead of 0. > Is there a good way to make sure that all callers will follow this rule > going forward? Perhaps, memblock_find_in_range_node() should emit some > message if 0 is passed when current_order is low to high and the boot > option is specified?
How about set this as the default rule:
When using from low to high order, always allocate memory from current_limit_low.
So far, I think only movablenode boot option will use this order.
> > Similarly, I wonder if we should have a check to the allocation size to > make sure that all allocations will stay small in this case. >
We can check the size. But what is the stragety after we found that the size is too large ? Do we refuse to allocate memory ? I don't think so.
I think only relocate_initrd() and reserve_crachkernel() could allocate large memory. reserve_crachkernel() is easy to reorder, but reordering relocate_initrd() is difficult because acpi_initrd_override() need to access to it with va.
I think on most servers, we don't need to do relocate_initrd(). initrd will be loaded to mapped memory in normal situation. Can we just leave it there ?
Thanks.
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