(2012/07/25 0:55), Cong Wang wrote: > On Mon, 2012-07-23 at 20:22 +0900, Takao Indoh wrote: >> (2012/07/23 19:00), Dave Young wrote: >>> On 07/17/2012 11:15 AM, Takao Indoh wrote: >>> >>>> Hi Cong, >>>> >>>> When I tested kdump with 3.5.0-rc6 kernel, I found a problem of kdump >>>> kernel's panic in find_early_table_space(). >>>> >>>> init_memory_mapping: [mem 0x00000000-0x36ffafff] >>>> Kernel panic - not syncing: Cannot find space for the kernel page tables >>>> Pid: 0, comm: swapper Not tainted 3.5.0-rc6 #17 >>>> Call Trace: >>>> [<ffffffff8158549b>] panic+0xb8/0x1c8 >>>> [<ffffffff8158565d>] ? printk+0x48/0x4a >>>> [<ffffffff8157304c>] init_memory_mapping+0x46c/0x530 >>>> [<ffffffff818a73c7>] setup_arch+0x669/0xb0e >>>> [<ffffffff8158565d>] ? printk+0x48/0x4a >>>> [<ffffffff818a3a1f>] start_kernel+0x9b/0x34a >>>> [<ffffffff818a332d>] x86_64_start_reservations+0x131/0x136 >>>> [<ffffffff818a341f>] x86_64_start_kernel+0xed/0xf4 >>>> >>>> In find_early_table_space(), a kernel tries to find free area below 512M >>>> for pgtable using memblock_find_in_range, but it fails because kdump >>>> kernel does not have enough free space below 512M due to the memmap >>>> restriction. This is the memmap option specified against kdump kernel >>>> when crashkernel=128M. >>>> >>>> memmap=560K at 64K memmap=130492K at 770608K >>>> >>>> Only 560KB area is available and it is not sufficient for pgtable (it >>>> seems that about 1.8MB area is needed for pgtable). This problem is >>>> fixed by your revert patch. I hope this patch gets merged. >>> >>> >>> I can reproduce this issue as well, probably related to some x86 mm init >>> commits, this alloc failure does not happen with reverting below commits: >>> >>> bd2753b2dda7bb43c7468826de75f49c6a7e8965 >>> 722bc6b16771ed80871e1fd81c86d3627dda2ac8 >> Yeah, my result of bisect is as follows and at first I thought the >> commit 722bc6 caused this regression. >> >> 722bc6b16771ed80871e1fd81c86d3627dda2ac8 is the first bad commit >> commit 722bc6b16771ed80871e1fd81c86d3627dda2ac8 >> Author: WANG Cong <xiyou.wangcong at gmail.com> >> Date: Mon Mar 5 15:05:13 2012 -0800 >> >> IIUC, this commit just fixes a bug of counting pgtable entries. As the >> result, another problem came up to the surface. In the case of my >> machine(16GB memory), before applying 722bc6, find_early_table_space() >> requests about 12KB free area and it can be got from 560K at 64K area >> luckily. I think the size find_early_table_space() requests was a bug. >> After the bug is fixed by the commit 722bc6, find_early_table_space() >> requires 1.8MB area and it fails as I wrote. > > Thanks for tracking this, Takao! > > I bet you are using x86_64 not x86 PAE? If so, could you try this patch > https://patchwork.kernel.org/patch/1195751/ > ? I already reviewed it. Great, I applied it and now kdump works. Thanks! Thanks, Takao Indoh
