Re: [Xen-ia64-devel] PATCH: xencomm [2]

[Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>]

Hi, Aron

I think this issue do not relate xencomm and copy_from/to_user.
This issue is caused by page_alloc of net/blkbk module.

order:8 is too big.
After forked and terminated some process,
alloc_page() of oder:8 almost fail.

So builtin module don't have this issue because none of process is created 
before initialization of these module.

The solutions of this issue are:
1. fix memory allocation of blkbk, netbk
2. builtin blkbk, netbk
3. allocate big memory to dom0

See the following code.
static int __init blkif_init(void)
{
        struct page *page;
        int i;

        if (!is_running_on_xen())
                return -ENODEV;

        mmap_pages            = blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST; 
<<<< too big

        page = balloon_alloc_empty_page_range(mmap_pages); <<<<< alloc_page()
        if (page == NULL)
                return -ENOMEM;
        mmap_vstart = (unsigned long)pfn_to_kaddr(page_to_pfn(page));
        
        
Best Regards,

Akio Takebe

>Hi Tristan,
>
>Tristan Gingold wrote:  [Thu Sep 28 2006, 07:33:28AM EDT]
>> My tests were booting dom0+2*dom_U (using netbk, blkbk and netloop as 
>> modules), and doing ping+wget from domU_1.
>
>I tested these patches on the Fedora rawhide kernel, but I still see
>the memory allocation failure when trying to load the netbk or blkbk
>modules in dom0.
>
>I thought that these patches would solve this problem, but the netbk
>module isn't touched.  Could you comment?
>
>Thanks,
>Aron
>
>modprobe: page allocation failure. order:8, mode:0xd0
>
>Call Trace:
> [<a00000010001c8e0>] show_stack+0x40/0xa0
>                                sp=e00000001fdffc20 bsp=e00000001fdf9240
> [<a00000010001c970>] dump_stack+0x30/0x60
>                                sp=e00000001fdffdf0 bsp=e00000001fdf9228
> [<a00000010010b220>] __alloc_pages+0x500/0x540
>                                sp=e00000001fdffdf0 bsp=e00000001fdf91b0
> [<a00000010010b310>] __get_free_pages+0xb0/0x140
>                                sp=e00000001fdffe00 bsp=e00000001fdf9188
> [<a0000001003c7400>] balloon_alloc_empty_page_range+0x80/0x400
>                                sp=e00000001fdffe00 bsp=e00000001fdf9140
> [<a0000002000cc190>] netback_init+0x190/0x5c0 [netbk]
>                                sp=e00000001fdffe30 bsp=e00000001fdf9108
> [<a0000001000d1dc0>] sys_init_module+0x180/0x400
>                                sp=e00000001fdffe30 bsp=e00000001fdf9098
> [<a000000100014100>] ia64_ret_from_syscall+0x0/0x40
>                                sp=e00000001fdffe30 bsp=e00000001fdf9098
> [<a000000000010620>] __start_ivt_text+0xffffffff00010620/0x400
>                                sp=e00000001fe00000 bsp=e00000001fdf9098
>Mem-info:
>DMA per-cpu:
>cpu 0 hot: high 42, batch 7 used:14
>cpu 0 cold: high 14, batch 3 used:13
>DMA32 per-cpu: empty
>Normal per-cpu: empty
>HighMem per-cpu: empty
>Free pages:       22416kB (0kB HighMem)
>Active:5579 inactive:9841 dirty:269 writeback:0 unstable:0 free:1401 slab:
>1139 mapped:1143 pagetables:151
>DMA free:22416kB min:2896kB low:3616kB high:4336kB active:89264kB inactive:
>157456kB present:524288kB pages_scanned:0 all_unreclaimable? no
>lowmem_reserve[]: 0 0 0 0
>DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB
> pages_scanned:0 all_unreclaimable? no
>lowmem_reserve[]: 0 0 0 0
>Normal free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:
>0kB pages_scanned:0 all_unreclaimable? no
>lowmem_reserve[]: 0 0 0 0
>HighMem free:0kB min:512kB low:512kB high:512kB active:0kB inactive:0kB 
>present:0kB pages_scanned:0 all_unreclaimable? no
>lowmem_reserve[]: 0 0 0 0
>DMA: 169*16kB 96*32kB 50*64kB 21*128kB 8*256kB 5*512kB 4*1024kB 1*2048kB 0*
>4096kB 0*8192kB 0*16384kB = 22416kB
>DMA32: empty
>Normal: empty
>HighMem: empty
>Swap cache: add 0, delete 0, find 0/0, race 0+0
>Free swap  = 2031584kB
>Total swap = 2031584kB
>Free swap:       2031584kB
>32768 pages of RAM
>13277 reserved pages
>5037 pages shared
>0 pages swap cached
>13 pages in page table cache
>
>
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