From owner-freebsd-hackers Wed Jan 29 11:10:46 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id LAA15725 for hackers-outgoing; Wed, 29 Jan 1997 11:10:46 -0800 (PST) Received: from sendero.i-connect.net ([206.190.144.100]) by freefall.freebsd.org (8.8.5/8.8.5) with SMTP id LAA15720 for ; Wed, 29 Jan 1997 11:10:41 -0800 (PST) Received: (qmail 3901 invoked by uid 1000); 29 Jan 1997 20:09:59 -0000 Message-ID: X-Mailer: XFMail 1.1-alpha [p0] on FreeBSD Content-Type: text/plain; charset=iso-8859-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 Date: Wed, 29 Jan 1997 11:13:14 -0800 (PST) Organization: iConnect Corp. From: Simon Shapiro To: hackers@freebsd.org Subject: More 2.2-BETA goodies... Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk [ I am cross-posting this to scsi as well, as some of the issues here are SCSI related and I am not sure that readership is overlapping... ] Hi Y'all, Since we are all bored with nothing better to do I decided to burden this nice quorum with some more good ways to use 2.2-BETA. Maybe you can clarify some of them for me: 1. An easy way to panic the system: * Put ``devfs /devs devfs rw 0 0'' in /etc/fstab * Do ``mount -a'' * Do ``mount -a'' (again) * Do ``df'' - You will see /devs mounted twice. Actually you will see /kern and /dev twice if you setup kernfs and/or fdesc. * do ``umount /devs'' You will get a nice little panic with a complaint about dangling inodes. 2. Not a show stopper. More of a question. Under HEAVY disk I/O, with an AHA-2940W, you see all keyboard, mouse, modem activity freeze for few seconds and then resume. I suspected SCSI timeouts, but saw no kernel or driver complaints. It appears as if the system stops processing interrupts for a while. Quiet SCSI timeout (no error messages)? 3. Back to the Iomega Jaz: If it spins down (it likes to do that), and then you try to access it (say mount a file system), you get dropped the kernel debugger (``db>''), with ``.. sd... no slices...'' error message. Now, if you are lucky, you were not in X11, and can see the ``db>'' on the screen. All you need to do is type ``c'' once and all will be well. If you do it too quickly, you will repeat the event. Is this problem: a. The aic7xxx driver timing out too soon b. The SCSI code above the driver deciding to timeout too soon c. Iomega not building hardware to FreeBSD specs :-) If, on the other hand, you were in an X11 session, you are hosed. I think the kernel debugger stops interrupts at this point. What is the way to get at the debugger at this point. Aside from doing the proper thing, which is to configure a serial console, etc. 4. Pppd drops the connection, without warning, under very heavy load. 5. Question: Using xperfmon++ (cool), one observes that a system equipped with AHA2940W enjoys about 3-15 times as many interrupts/sec as disk transfers/sec. The system, does nothing but SCSI right now (cvs checkout in parallel with a tape backup (cpio, I know...). Nothing else. Assumin the #9 S3 card generates no interrupts, keeping my hands off the keyboard and mouse, no Ethernet traffic, no PPP traffic; The system does a peak of 246 disk T/s and about 625 interrupts/sec. Discounting 100 interrupts for the heartbeat, We still have two interrupts per sec charged to the disk I/O. Under HEAVY load, the numbers climb logarithmically; Up to 300 T/s with over 2,500 I/s. Heavy disk load in this note means 8``st'' threads in parallel. So that xperfmon++ will say 300+ T/s, which seems to be the maximum the AHA2940 can sustain. Ts is a Seek Test program we use to excite disks and stress them at the same time. It generates a random (or sequential) stream of I/O requests to a file/device and then measures how it does. It can either read or write, or read-modify-write and do a whole set of nifty things. If there is interest, I can post it. It runs on Slowlaris 2.5.1, linux 2.x and FreeBSD 9of courcse). We prefer it to others because it does true random seeks, very accurate and I wrote it, so it must be good :-). It is also short! Simon