/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ if (filp->f_flags & O_DIRECT) { loff_t size; struct address_space *mapping; struct inode *inode;
在 Linux 当中文件系统千奇百种，比较常见的有 EXT3、EXT4，还有基于内存的 ramfs、tmpfs 和基于网络的 nfs，和基于用户态的 fuse，当然 fuse 应该不能完全的文件系统，只能算是一个能把文件系统实现放到用户态的模块，满足了内核文件系统的接口，他们都是文件系统的一种实现。这个 wiki 上列出了很多 Linux 的文件系统类型。
图中展示了一个硬链接代表着 bc 和 ab 的 dentry 指向了同一个inode，硬链接是不同 dentry 指向同一个inode，这也是为什么硬链接不能夸文件系统，因为inode是属于特定文件系统的。 图中其实inode是串联在super_block上的，super_block维护了文件系统中`inodes，因为画上去太乱了所以省略了。
// A bucket for a Go map. type bmap struct { tophash [bucketCnt]uint8 // 这里的bucetCnt是8,是个固定值,每个桶跟8个k-v对. // 先是8个key,后是8个value. // 最后是一个overflow指针指向串联的bucket. }
而hmap表示如下,其实就是一个头信息.
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// A header for a Go map. type hmap struct { flags uint8 // 一些标志j B uint8 // bucket数量的log_2 hash0 uint32 // hash 种子
// A Section represents a single section in an ELF file. type Section struct { SectionHeader
// Embed ReaderAt for ReadAt method. // Do not embed SectionReader directly // to avoid having Read and Seek. // If a client wants Read and Seek it must use // Open() to avoid fighting over the seek offset // with other clients. io.ReaderAt sr *io.SectionReader }
func f(a float64) float64 { return 4.0/(1.0 + a * a) } func chunk(start, end int64, c chan float64) { var sum float64 = 0.0 for i:= start; i < end; i++ { x := h * (float64(i) + 0.5) sum += f(x) } c <- sum * h } func main() { runtime.GOMAXPROCS(np); h = 1.0/float64(n) ..//start timing c := make(chan float64, np) for i:=0; i < np; i++ { go chunk(int64(i)*n/int64(np), (int64(i)+1)*n/int64(np), c) } for i:=0; i < np; i++ { pi += <-c } ...//end timing }
var h,v [vp][vp] chan int var finish chan int ..//declare other variables and constants func creatChan() { for i:=0; i < vp; i++ { for j:=i; j < vp; j++ { if j < vp-1 {h[i][j] = make(chan int, 1)} if i > 0 {v[i][j] = make(chan int, 1)} } } } func mst(i,j int) { ... // the same as in the sequetial code } func chunk(i,j int) { var bb int il := (i * (n+1))/vp //block-low for i ih := ((i+1) * (n+1))/vp - 1 //block-high for i jl := (j * (n+1))/vp //block-low for j jh := ((j+1) * (n+1))/vp - 1 //block-high for j if i < j { // not a tile on the diagonal <-h[i][j-1] // receive from the left <-v[i+1][j] // receive from below } for ii:=ih; ii >= il; ii-- { if i==j { bb = ii } else { bb = jl } for jj:=bb; jj <= jh; jj++ { mst(ii,jj) } } if j < vp-1 {// not a tile on the right border h[i][j] <- 1 } if i > 0 { // not a tile on the top border v[i][j] <- 1 } if i==0 && j==vp-1 {//the last tile finish <- 1 } } func main() { ...//read flags runtime.GOMAXPROCS(np) ... //start timing creatChan() finish = make(chan int, 1) for d:=0; d < vp; d++ {//sub-diagonal of j=i+d for i:=0; i+d<vp; i++ { go chunk(i, i+d) } } <-finish ....//end timing }
[1] Shameen Akhter and Jason Roberts. Mutli-Core Programming: Increasing Performance through Software Multi-threading. Intel Press, 2006.
[2] Edward A. Lee. The problem with threads. IEEE Computer, 39(5):33–42, May 2006.
[3] Go Team.The Go programming language specification.Technical Report http://golang.org/doc/doc/go spec.html,Google Inc., 2009.
[4] C.A.R. Hoare. Communication Sequential Processes.Prentice Hall, 1985.
[5] Michael J. Quinn. Parallel Programming in C with MPI and OpenMP. McGraw-Hill, 2004.
[6] Thomas H. Corman, Charles E. Leiserson, Ronald L.Rivest, and Clifford Stein. Introductions to Algorithms,2nd Edition. McGraw-Hill Book Company, 2001.
[7] Sara Baase and Allen Van Gelder. Computer Algorithms: Introduction to Design and Analysis (3rd Ed).Addison-Wesley, 2000.
