Date: Sat, 14 Jul 2012 11:39:43 -0400 From: Justin Hibbits <chmeeedalf@gmail.com> To: mdf@freebsd.org Cc: freebsd-current <freebsd-current@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: panic with DEBUG_MEMGUARD on PowerPC Message-ID: <E7611D3D-806F-4BA1-9B83-6C903D23D6EB@gmail.com> In-Reply-To: <CAMBSHm-CM0hc2Cu=C-zf7ArENqVz9iOHCjb0wMSPCnYQbXKqdA@mail.gmail.com> References: <A3CD63CD-694A-48F5-B0F7-9C8923AFCB90@gmail.com> <CAMBSHm-5Xix46MaYAwBek6hWvcOHZ7%2BR_4cpdG5SH_5RD7difQ@mail.gmail.com> <307005B6-C8E5-4DCF-BD10-6BC79D8C2FE3@gmail.com> <CAMBSHm-CM0hc2Cu=C-zf7ArENqVz9iOHCjb0wMSPCnYQbXKqdA@mail.gmail.com>
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On Jul 13, 2012, at 12:20 AM, mdf@freebsd.org wrote: > On Thu, Jul 12, 2012 at 6:33 PM, Justin Hibbits > <chmeeedalf@gmail.com> wrote: >> On Jul 12, 2012, at 9:11 PM, mdf@freebsd.org wrote: >> >>> On Thu, Jul 12, 2012 at 4:43 PM, Justin Hibbits <chmeeedalf@gmail.com >>> > >>> wrote: >>>> >>>> When tracking down a panic exposed by INVARIANTS, I tried setting >>>> DEBUG_MEMGUARD, so I could find the culprit that's trashing freed >>>> memory. >>>> However, this causes a panic at bootup. It shows up right after >>>> the >>>> first >>>> WARNING: WITNESS message, with the following: >>>> >>>> Tracing, and printf() debugging, I see arguments to >>>> vm_map_findspace(): >>>> start: 0xD0000000, length: 4246446080, and map->max_offset = >>>> 4026531839. >>>> >>>> Beyond that, I'm lost with tracking this down. Machine is a dual >>>> processor >>>> PowerPC G4, with 2GB RAM. >>> >>> >>> The length is 0xFD1BA000 which is almost 4GB. Asking for 4GB of >>> virtual space for 2GB of RAM sounds about right (it's been a while >>> since I was in this code), unless this is a 32-bit kernel, in which >>> case it'd be too much since there isn't that much virtual space >>> available. >>> >>> So, is the kernel 32-bit? What are the values used and returned by >>> memguard_fudge()? The intent of that routine is to get kmeminit() >>> to >>> allocate a larger map so memguard can use part of it for private >>> virtual addresses. But it shouldn't be asking for "too much"; i.e. >>> the intent was to check both physical and virtual space available >>> and >>> be greedy, but not too greedy. >>> >>> There were some issues with that code for some platforms that e.g. >>> didn't define a VM_KMEM_SIZE_MAX, but alc@ fixed that in r216425. >> >> It is a 32-bit kernel, on 32-bit hardware. The values for >> memguard_fudge >> are (defaults): >> >> tmp: 4246446080, vm_kmem_size: 117440512, vm_kmem_size_max: 0 >> >> When setting vm.kmem_size/vm.kmem_size_max to 2GB they are: >> >> tmp: 2147483648, vm_kmem_size: 214793648, vm_kmem_sizee_max: >> 2147483648 (all >> 2GB). >> >> But the start and map->max_offset remain the same on all runs I make. > > memguard_fudge is still broken for 32-bit architectures with no > vm_kmem_max. In the absence of a km_max to limit the value, we > essentially use twice the physical memory for the virtual limit. But > with 2GB on a 32-bit machine, this requires 4GB of virtual space. > > Setting vm_kmem_size_max to 2GB should work; I'd expect to see > tmp=about 200MB, which is much larger than the input 112MB but the > allocation should work. But I don't really know what else PowerPC has > need of for virtual space, so that still could be too large. > > You can try smaller values of vm_kmem_size_max, like 1GB or 512MB. > You shouldn't need to set vm_kmem_size at all. At some point the > added space for the memguard_map will be small enough that the > kmem_suballoc will work. > > Hmm, what is the min_offset and max_offset of kernel_map when the call > to memguard_fudge is made? > > Thanks, > matthew Without setting vm.kmem_size/vm.kmem_size_max, I see the following: map: 0x1000000, min_offset: 0xD0000000, max_offset: 0xEFFFFFFF It does boot when I set vm.kmem_size=256M/vm.kmem_size_max=512M. When I tried 512M/1024M, it panicked at the same place -- kmem_suballoc from kmeminit. So it looks like I have to set vm.kmem_size/vm.kmem_size_max way back in order for it to boot with memguard(9). - Justin
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