Article Source: TSINGHUA
Sender: Forest (light cold building ~ VL), letter area: UNIX Title: Significance of the core parameters of SCO UNIX system [reproduced] Send Station: BBS Shuimu Tsinghua Station (Fri Oct 29 09:10:50 1999) , Disk and buffer NDisk is the number of disk drives on the system. It is set when booted. NBUF The number of 1K system buffers allocated during boot. These buffers are in a data cache. This data cache is a memory array containing disk file information. The hit rate of the cache increases with the increase in the buffer. The hit of the cache reduces the access to the disk and thus improves the overall performance of the system. This parameter value is typically in the range of 100 to 600. Each buffer contains 1076 bytes. The number of HASH queues (NHBUF) should increase with the system buffer, so opt optimal performance. NPBUF specifies how many physical I / O buffers to be assigned. Each read / write activity requires an I / O buffer. Each inlet buffer. The first entrance contains 52 bytes. The default value of this parameter is 20. NHBUF is specified as a 1K buffer allocation how many Hash queues. This is to search for a given device number and a buffer buffer, so it is not necessary to perform linear searches in the renovation buffer queue. This value must be a power of 2. Each inlet contains 12 bytes. The value of NHBUF must be selected, and the NBUF is removed by NHBUF is about 4. (View NBUF value in file / usr / adm / messages, it is determined and displayed when booted.) CTBufSize is the size of the tape (QiC-11, QiC-24) buffer unit in kbye. It should be 32 to 256. It is the size of the static buffer allocated in initialization. Below is a reasonable value corresponding to the corresponding environment: 32K bare minimum: not enough to the data stream. 64K allows data streams (beneficial for systems with small memory) or using small tapes (not critical to performance). 96K ratio of low-level configuration, if the default value is used too much, it will be reduced. 128K Default: Good performance compromise configuration value. The 192K ratio of high levels of high levels, if the default value is too poor, it will increase this value. 256k maximum. MaxBUF allows the maximum number of buffers in the cache. This is the number of buffers in the core. If the required buffer number is less than this value, the configuration is automatically configured according to the size of the memory. If NBUF is not 0, then the NBUF buffer will be accurately configured, while MaxBuf is not necessarily greater than NBUF. If NBUF is 0, the core will be able to configure maximum MaxBuf buffer. OmaableBUF The number of transport buffers required for the transfer buffer required for DMA requests greater than 16MB. It must be a value of 4 to 128. The default is 16. NAUTOUP The automatic update of the file system specifies the life of the buffer in seconds. It will be written to the hard disk when the content in a system buffer has resided from the NAUTOUP parameter for such a long time. If you specify a smaller value, the system's reliability will increase because of the more frequent content written in the buffer, but system performance will decrease. Specifying a large value will increase system performance, but to reduce BDFLUSHR to check the frequencies that specify in seconds to write the contents of the contents of the file system buffer. The range is from 1 to 300. The default is 30 seconds. This parameter controls the activities of the BDFlush daemon. Putbufsz Specifies the size of the annular buffer Putbuf, and the Putbuff contains the last few Putbufsz characters written by the operating system to the console. The contents of Putbuf can be seen using Crash (ADM). PiOMAP determines the size of the mapping inlet used by the core programmable I / O (PIO) decomposition routine. This routine can allow the device driver to complete the programmable I / O operation of the large data block by breaking the large data block into a small data unit and interrupt level. Users should not modify this parameter.
