Path: utzoo!attcan!lsuc!canrem![glen_lalonde@canrem.uucp] From: glen_lalonde@canrem.uucp (glen lalonde) Newsgroups: comp.os.minix Subject: macminix Message-ID: <1991Jan13.1046.1369@canrem.uucp> Date: 13 Jan 91 05:18:49 GMT Reply-To: "glen lalonde" Organization: Canada Remote Systems Lines: 40 My setup is a Mac+ with 4MB. I wanted to enhance the speed of disk IO in MacMinix. First off I found the following. cat a 176K file to /dev/null from floppy takes real 15, user .1 sys 3.8. For a 337K from floppy it takes 30,1.8 and 7.0 Now from hard disk for a 243K file to /dev/null it takes real 16, u 1.4, sys 14.6 I don't understand why for sys the value from the hard disk is so high. Now I do understand that the larger real time for the floppy is just a result of it being a slower device. Also recall that the floppy and hard disk use the exact same driver code. You can connect /dev/fd0 to a hard disk file if you want. Anyways here is the good stuff. What I wanted to do is alter the way MacMinix does IO, now it opens a file and requests reads from the file, the file being the minix file system. Thinking that this is slow, since the macos will have to lookup where on the disk the sector for that pos in the file is, I alter the floppy task for /dev/fd1 to call the MacOS device driver for the floppy. Thus we don't get the overhead of going through a file. This was easy to do since you still just call PBRead, PBWrite. It only takes about 20 lines of changes. I formated a 3.5 inch disk and made sure that all the used sectors were at the front. They I added an offset of 42*512(42 sectors) to the pos to read when calling the .Sony device driver. I was thinking this would result in much faster IO, but it DID NOT. There was just about NO change in the IO rate! I only can conclude that the real time to do IO must be so large that the overhead in going through a MacOS file is small in percent terms. Now my change might be better for a hard disk since the physical IO does not take as long and thus the macOS file overhead might be a larger %. The only problem is setting up my harddisk to have a large continuous number of sectors that I can use is not easy. Anyways it was an interesting project. All mac io in macminix is done async, what does that do? Does the mac allocate processor time at vertical retrace time to do the IO? Recall on the mac+ there is no non-processor related IO(no real dma). -- Canada Remote Systems. Toronto, Ontario NorthAmeriNet Host