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March 31, 2005
愚人节快乐
黑色的愚人节玩笑
Posted by Roy at 11:13 PM | Comments (0)
March 20, 2005
DMA, DVMA, IOMMU, scatter-gather...
http://bama.ua.edu/cgi-bin/man-cgi?ddi_dma_attr+9S
Some platforms, such as SPARC systems, support
what is called Direct Virtual Memory Access
(DVMA). On these platforms, the device is pro-
vided with a virtual address by the system in
order to perform the transfer. In this case, the
underlying platform provides an IOMMU, which
translates accesses to these virtual addresses
into the proper physical addresses. Some of these
platforms also support DMA.
DDI_DMA_FORCE_PHYSICAL indicates that the system
should return physical rather than virtual I/O
addresses if the system supports both. If the
system does not support physical DMA, the return
value from ddi_dma_alloc_handle(9F) will be
DDI_DMA_BADATTR. In this case, the driver has to
clear DDI_DMA_FORCE_PHYSICAL and retry the opera-
tion.
http://docs.sun.com/app/docs/doc/816-4854/6mb1o3aeg?a=view
The platform on which the device operates provides either direct memory access (DMA) or direct virtual memory access (DVMA).
On platforms that support DMA, the system provides the device with a physical address in order to perform transfers. In this case, the transfer of a DMA object can actually consist of a number of physically discontiguous transfers. An example is when an application transfers a buffer that spans several contiguous virtual pages that map to physically discontiguous pages. To deal with the discontiguous memory, devices for these platforms usually have some kind of scatter-gather DMA capability. Typically, x86 systems provide physical addresses for direct memory transfers.
On platforms that support DVMA, the system provides the device with a virtual address to perform transfers. In this case, memory management units (MMU) provided by the underlying platform translate device accesses to these virtual addresses into the proper physical addresses. The device transfers to and from a contiguous virtual image that can be mapped to discontiguous physical pages. Devices that operate in these platforms do not need scatter-gather DMA capability. Typically, SPARC platforms provide virtual addresses for direct memory transfers.
http://www.buyya.com/microkernel/chap6.pdf
pp. 6
Posted by Roy at 05:02 PM | Comments (0)
March 17, 2005
About Hashtable and generics in Java
I'm not familiar with Java, so I didn't quite understand all the stuffs here. Anyway it helps:
http://forums.java.sun.com/thread.jspa?threadID=590293&tstart=15
Posted by Roy at 11:15 PM | Comments (0)
March 16, 2005
哀
ytht，smth，什么时候轮到ustc
Posted by Roy at 07:13 PM | Comments (0)