[Xen-devel] difference between DMA heap and dom heap

[ruby young <9907yruby@xxxxxxxxx>]

Hi，all~

I have a question on machine memory. There is pagealloc_keyhandler function in page_alloc.c file. It has below lines:

 

    while ( ++zone < NR_ZONES )
    {
        if ( (zone + PAGE_SHIFT) == dma_bitsize )
        {
            printk("    DMA heap: %lukB free\n", total << (PAGE_SHIFT-10));
            total = 0;
        }

        if ( (n = avail_heap_pages(zone, zone, -1)) != 0 )
        {
            total += n;
            printk("    heap[%02u]: %lukB free\n", zone, n << (PAGE_SHIFT-10));
        }
    }

    printk("    Dom heap: %lukB free\n", total << (PAGE_SHIFT-10));

 

we can see the free space of DMA heap is the sum of free pages from zone[1] to zone [20], and the dom heap is always 0.

How about DMA heap and Dom heap mean? Why should divide the heap into DMA heap and Dom heap?

 

Thanks

 

                                                                                  Ruby Young

 

--
Best wishes

杨漾
北京航空航天大学计算机学院体系结构研究所
电话:010-82338059-132
邮件:9907yruby@xxxxxxxxx
地址：北京市海淀区学院路37号北京航空航天大学新主楼 G座1026
--------------------------------------------------------------------------------
Yang Yang
Institute of Computer Architecture and System
BeiHang University（BUAA）
Tel: (86-10)82338059-132
Email: 9907yruby@xxxxxxxxx
Addr: Room 1026,Building G,The New Main Building,37# Xueyuan Rd.,Haidian District, Beijing 100083, PRC

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel