From 509a80c49c512ac88bd67b981145f925a306111b Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 17 Oct 2007 18:04:34 +0200 Subject: x86: fix CONFIG_PAGEALLOC related boot hangs/OOMs if CONFIG_PAGEALLOC is enabled then X86_FEATURE_PSE is disabled and all the kernel physical RAM pagetables are set up as 4K pages. This is needed so that CONFIG_PAGEALLOC can do finegrained mapping and unmapping of pages. as a side-effect though, the total size of memory allocated as kernel pagetables increases significantly. All these pagetables are allocated via alloc_bootmem_low_pages(), straight out of the lowmem DMA pool. If the system has enough RAM and a large kernel image then almost all of the 16 MB lowmem DMA pool is allocated to the image and to pagetables - leaving no space for __GFP_DMA allocations. this results in drivers failing and the bootup hanging: swapper invoked oom-killer: gfp_mask=0x80d1, order=0, oomkilladj=0 [<4015059f>] out_of_memory+0x17f/0x1c0 [<40151f3c>] __alloc_pages+0x37c/0x3a0 [<40168cd7>] slob_new_page+0x37/0x50 [<40168dff>] slob_alloc+0x10f/0x190 [<40169010>] __kmalloc_node+0x80/0x90 [<405a17e3>] scsi_host_alloc+0x33/0x2c0 [<405a1a82>] scsi_register+0x12/0x60 [<40d5889e>] aha1542_detect+0x9e/0x940 [<405c5ba5>] ultrastor_detect+0x265/0x5f0 [<401352f5>] getnstimeofday+0x35/0xf0 [<40d58751>] init_this_scsi_driver+0x41/0xf0 [<40d0b856>] kernel_init+0x136/0x310 [<40d58710>] init_this_scsi_driver+0x0/0xf0 [<40d0b720>] kernel_init+0x0/0x310 [<40105547>] kernel_thread_helper+0x7/0x10 ======================= the fix is to first allocate from above the DMA pool, and if that fails (for example due to it being a machine with less than 16 MB of RAM), allocate from the DMA pool as a fallback. With this fix applied i was able to boot a PAGEALLOC=y kernel that would hang before. Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/mm/init_32.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index dda4e83649a..e4e37d4f4c5 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -85,13 +85,20 @@ static pmd_t * __init one_md_table_init(pgd_t *pgd) static pte_t * __init one_page_table_init(pmd_t *pmd) { if (!(pmd_val(*pmd) & _PAGE_PRESENT)) { - pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE); + pte_t *page_table = NULL; + +#ifdef CONFIG_DEBUG_PAGEALLOC + page_table = (pte_t *) alloc_bootmem_pages(PAGE_SIZE); +#endif + if (!page_table) + page_table = + (pte_t *)alloc_bootmem_low_pages(PAGE_SIZE); paravirt_alloc_pt(&init_mm, __pa(page_table) >> PAGE_SHIFT); set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE)); BUG_ON(page_table != pte_offset_kernel(pmd, 0)); } - + return pte_offset_kernel(pmd, 0); } -- cgit v1.2.3