有人说/tmp 是物理内存，是这样的吗？

cuwiner

今天SUN的工程师过来这么说，我觉得有点奇怪，好象只有SUN的/TMP是物理内存，别的OS的/TMP是磁盘

briangao

Nope. /tmp mounts your virtual swap space, which is the physical swap space + the free memory at that time. So the Sun engineer is half right. In Solaris /tmp is not your ordinary hard disk space

cuwiner

原帖由 briangao 于 2007-3-14 10:48 发表\r\nNope. /tmp mounts your virtual swap space, which is the physical swap space + the free memory at that time. So the Sun engineer is half right. In Solaris /tmp is not your ordinary hard disk space

\r\n\r\n  谢谢，在系统中我看了一下\r\nswap                   798M    20K   798M     1%    /var/run\r\nswap                   798M     0K   798M     0%    /tmp\r\n\r\n有2个疑问\r\n\r\n1  有2个SWAP，一个就是你说的 /TMP，这个是物理内存和物理swap space的混合体，但是还有另外一个/var/run，这个就应该全部都是物理磁盘把，有2个SWAP是不是为了负载平衡\r\n\r\n2  听说如果在/TMP里面放很多临时文件的话，把/TMP占满后，系统就会很慢，处于有2个SWAP来实现负载平衡的需要，/var/run所在的SWAP好象没有发挥什么作用？

briangao

1  有2个SWAP，一个就是你说的 /TMP，这个是物理内存和物理swap space的混合体，但是还有另外一个/var/run，这个就应该全部都是物理磁盘把，有2个SWAP是不是为了负载平衡

\r\nNo, Both /var/run and /tmp points to the same virtual swap space. /var/run is writable by system process and root user only. /tmp is writable by all users\r\n\r\n

2  听说如果在/TMP里面放很多临时文件的话，把/TMP占满后，系统就会很慢，处于有2个SWAP来实现负载平衡的需要，/var/run所在的SWAP好象没有发挥什么作用？

\r\nYes, it you fill up /tmp, it is equivalent that you use up all the memory and machine will start to swap.

cuwiner

原帖由 Solaris12 于 2007-3-14 11:07 发表\r\n\r\n\r\n\r\n很多应用程序喜欢用/var/run存放临时文件，所以，/var/run是swap可以加快速度。\r\n\r\n关于tmp，可以看：\r\nbash-3.00# man tmpfs\r\nReformatting page.  Please Wait... done\r\n\r\nFile Systems                  ...

\r\n\r\n\r\n  谢谢\r\n\r\n# df -n\r\n \r\n/var/run           : tmpfs   \r\n/tmp               : tmpfs \r\n\r\n\r\n  从这个里面看所有的SWAP都是同一种文件\r\n\r\ntmpfs is a  memory  based  file  system  which  uses  kernel resources relating to the VM system and page cache as a file system\r\n\r\n  从这个里面看，说tmpfs 是一种以MEMORY为基础的的文件系统，我不太明白这个是什么意思？\r\n\r\n  在我看的资料中，里面说有一个分区，一般都是C0T0D0S0做SWAP，那这个怎么和以MEMORY为基础的文件系统相矛盾？

cuwiner

原帖由 briangao 于 2007-3-14 11:18 发表\r\n\r\nNo, Both /var/run and /tmp points to the same virtual swap space. /var/run is writable by system process and root user only. /tmp is writable by all users\r\n\r\n\r\nYes, it you fill up /tmp, it is equ ...

\r\n\r\n\r\n  谢谢大师  \r\n\r\n  但是我还是不明白，这个physical swap space + the free memory表示什么意思？\r\n\r\n  难道说这个SWAP是物理磁盘和物理内存的混合体？只是这个对USER来说是透明的？

briangao

难道说这个SWAP是物理磁盘和物理内存的混合体？只是这个对USER来说是透明的？

\r\nYou can think of it as a concatenation of the swap partition (such as c0t0d0s1) on your hard disk and the free memory at that time, formated into one file system called swapfs. It is mounted under /tmp directory for convenience so that users and processes can use regular file system semantics to access the information. This kind of file system is called memory-based file system or pseduo file system. There are quite a few of such file systems in Solaris such as /proc.