From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 796766B0096 for ; Mon, 18 Jan 2010 17:56:36 -0500 (EST) From: Jiri Slaby Subject: [RFC 1/1] bootmem: move big allocations behing 4G Date: Mon, 18 Jan 2010 23:56:30 +0100 Message-Id: <1263855390-32497-1-git-send-email-jslaby@suse.cz> Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org Cc: hannes@cmpxchg.org, linux-kernel@vger.kernel.org, jirislaby@gmail.com List-ID: 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? -- 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org