Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [RFC 1/1] bootmem: move big allocations behing 4G | Date | Mon, 18 Jan 2010 23:56:30 +0100 |
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Hi, I'm fighting a bug where Grub loads the kernel just fine, whereas isolinux doesn't. I found out, it's due to different addresses of loaded initrd. On a machine with 128G of memory, grub loads the initrd at 895M in our case and flat mem_map (2G long) is allocated above 4G due to 2-4G BIOS reservation.
On the other hand, with isolinux, the 0-2G is free and mem_map is placed there leaving no space for others, hence kernel panics for swiotlb which needs to be below 4G.
I use the patch below, but it seems, from the code, like it won't work out for section allocations.
Any ideas?
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If there is a big amount of memory (128G) in a machine and 2G of low 4 gigs are reserved by BIOS, the rest of the "low" memory is consumed by mem_map with flat mapping enabled.
Consequent allocations with limit being 4G (e.g. swiotlb) fails to allocate and kernel panics.
Try to avoid that situation on 64-bit by allocating space bigger than 128M above 4G if possible. With that, mem_map is allocated above 4G and there is enough space for others (swiotlb) in low 4G. --- mm/bootmem.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/mm/bootmem.c b/mm/bootmem.c index 7d14868..365a0d1 100644 --- a/mm/bootmem.c +++ b/mm/bootmem.c @@ -486,6 +486,11 @@ static void * __init alloc_bootmem_core(struct bootmem_data *bdata, step = max(align >> PAGE_SHIFT, 1UL); + /* on 64-bit: allocate 128M+ at 4G if satisfies limit */ + if (BITS_PER_LONG == 64 && size >= (128UL << 20) && + (4UL << 30) + size < (max << PAGE_SHIFT)) + goal = 4UL << (30 - PAGE_SHIFT); + if (goal && min < goal && goal < max) start = ALIGN(goal, step); else -- 1.6.5.7
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