Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!mcsun!ukc!icdoc!qmw-cs!liam From: liam@cs.qmw.ac.uk (William Roberts;) Newsgroups: comp.unix.aux Subject: Re: NBUF and pstat Message-ID: <2859@redstar.cs.qmw.ac.uk> Date: 16 Jan 91 21:23:14 GMT References: <2657@dftsrv.gsfc.nasa.gov> Sender: usenet@cs.qmw.ac.uk Lines: 38 Nntp-Posting-Host: whitesand In <2657@dftsrv.gsfc.nasa.gov> jim@jagubox.gsfc.nasa.gov (Jim Jagielski) writes: >Currently, my kernel is built with NBUF being 0, meaning that 10% of >the free space at start-up is utilized for disk buffers. I want more. >The question is how many buffers are there??? >I would guess, using pstat, that NBUF is actually set to 1551 since >that is the value that pstat returns for buffers.... Is this right? I believe that you are right: certainly the comments in /usr/include/sys/var.h seem to agree with you, as does examination of various different machines I have to hand. On our machines we have SBUFSIZE set to 2048, NBUF set to zero, and we see 4 Meg => 135 buffers 5 Meg => 185 buffers (extra 40 for 1 Meg extra memory) 8 Meg => 339 buffers (extra 204 for 4 Meg extra memory) 204*2K = 408K which is pretty much 10% of 4 megabytes. The 5 Meg machine is a Mac II not a IIcx and has one of the infamous old EtherPort II ethernet cards, so the kernel is going to be a bit different and occupy a different amount of space, hence slightly fewer extra buffers than you might expect. Your figure of 1551 seems very high - let me guess: either you are running a 32 Megabyte machine, or you have SBUFSIZE set to 1024 and you are running a 16 Meg machine. For networking stuff there is also NMBUFS, which we set to 500, and 9 different NBLK* values associated with streams buffering, all of which are also types of "buffers" and affect the amount of memory you have available. -- William Roberts ARPA: liam@cs.qmw.ac.uk Queen Mary & Westfield College UUCP: liam@qmw-cs.UUCP Mile End Road AppleLink: UK0087 LONDON, E1 4NS, UK Tel: 071-975 5250 (Fax: 081-980 6533)