res@colnet.uucp (Rob Stampfli) (03/17/91)
In the User's Manual for the 3B1 Unix-PC, vers 3.5, there is a command called ktune(7), which allows one to tune certain Unix parameters in the kernel. One of the parameters is called npbuf: npbuf Number of buffer headers available in the raw I/O pool of headers Range: 4 up to system capacity. (Default: 16) Can someone give me more information on this parameter. When is one of these used? Are they consumed by uucico? rn? One per open fd (raw mode)? I thought I knew Unix, but this one is new to me. Tnx, -- Rob Stampfli, 614-864-9377, res@kd8wk.uucp (osu-cis!kd8wk!res), kd8wk@n8jyv.oh
john@chance.UUCP (John R. MacMillan) (03/19/91)
|In the User's Manual for the 3B1 Unix-PC, vers 3.5, there is a command called |ktune(7), which allows one to tune certain Unix parameters in the kernel. |One of the parameters is called npbuf: | |npbuf Number of buffer headers available in the raw I/O pool of headers | Range: 4 up to system capacity. (Default: 16) | |Can someone give me more information on this parameter. When is one of |these used? Are they consumed by uucico? rn? One per open fd (raw mode)? |I thought I knew Unix, but this one is new to me. Someone can correct me if I'm wrong (like I have to mention that :-) ), but I believe this is a small pool of buffer headers used on the occassions when the kernel wants to do device I/O using a buffer that isn't in the buffer cache, so doesn't have a header. I think this happens swapping pages, and also when a device is reading or writing a buffer directly out of user space (``raw'' I/O). I would think 16 would be plenty on a typical 3B1.