February 2002 - Darwin-kernel

Re: IOPanic ans assert not working ?
by Justin C. Walker 06 Feb '02

06 Feb '02

On Tuesday, February 5, 2002, at 03:43 PM, Sean McBride wrote: Justin C. Walker (justin(a)mac.com) wrote: If I understand you correctly, your computer freezes during boot. Is that correct? If so, have you tried booting 'verbosely' (CMD-v)? If not, what do you mean by "when I load my kernel..."? He means (I work with him, but he's gone home for the night...) that IOPanic is not behaving how he expects. We are expecting (maybe incorrectly) that when one calls IOPanic it will hose the kernel and spit out all that lovely text over whatever is on the screen. Itstead when calling IOPanic the machine just freezes. "when I load my kernel..." means using kextload on our kernel driver. (All the Windows people at our company have got us talking like them now... :( they say 'kernel' when they mean 'kernel driver') Thanks for clarifying that. It's a good thing Microsoft is continually reinventing the jargon we all use; otherwise, we'd all get sedentary and slothful. This is probably better for our long-term mental health than crossword puzzles. At least they haven't started writing it 'kernal'. IOPanic is just a wrapper around panic, for the benefit of those who don't feel comfortable with names that are all lower-case. Given that, the call, per se, does not 'hose the kernel'; it just stops processing. It should print the character string you pass it, and then grind ot a halt. The fact that it doesn't is a bit odd. Maybe you (he) mentioned this, but I've lost it: is this call in a kext? Is it just supposed to call IOPanic()? What version of Mac OS X (if any) are you using? And what version of the kernel (are you just using whatever came with it)? Next, can you set up and use the 2-machine debugger environment? If so, plant a breakpoint on IOPanic() and see if you actually get there. Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | Men are from Earth. | Women are from Earth. | Deal with it. *--------------------------------------*-------------------------------*

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Re: IOPanic ans assert not working ?
by Sean McBride 05 Feb '02

05 Feb '02

Justin C. Walker (justin(a)mac.com) wrote: >If I understand you correctly, your computer freezes during boot. Is >that correct? If so, have you tried booting 'verbosely' (CMD-v)? > >If not, what do you mean by "when I load my kernel..."? He means (I work with him, but he's gone home for the night...) that IOPanic is not behaving how he expects. We are expecting (maybe incorrectly) that when one calls IOPanic it will hose the kernel and spit out all that lovely text over whatever is on the screen. Itstead when calling IOPanic the machine just freezes. "when I load my kernel..." means using kextload on our kernel driver. (All the Windows people at our company have got us talking like them now... :( they say 'kernel' when they mean 'kernel driver') Thanks!

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Re: IOPanic ans assert not working ?
by Justin C. Walker 05 Feb '02

05 Feb '02

On Tuesday, February 5, 2002, at 09:49 AM, Francis Bouchard wrote: I had no response from darwin driver list s olet's try here... I'm at the point in my driver that I want to make sure I get proper assertions and IOPanic. I tried both in my code and defined MACH_ASSERT (to enable assert(false);). When I load my kernel, it just freeze my computer. No messages, nothing in the log no panic... Just a plain system freeze. I also tried IOPanic with a string message and it does the same freeze. No message, no stack trace. Do I have to do something special to get a message. Debugging is gonna be hard if I can't assert! If I understand you correctly, your computer freezes during boot. Is that correct? If so, have you tried booting 'verbosely' (CMD-v)? If not, what do you mean by "when I load my kernel..."? Regards, Justin -- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | If you're not confused, | You're not paying attention *--------------------------------------*-------------------------------*

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IOPanic ans assert not working ?
by Francis Bouchard 05 Feb '02

05 Feb '02

I had no response from darwin driver list s olet's try here... I'm at the point in my driver that I want to make sure I get proper assertions and IOPanic. I tried both in my code and defined MACH_ASSERT (to enable assert(false);). When I load my kernel, it just freeze my computer. No messages, nothing in the log no panic... Just a plain system freeze. I also tried IOPanic with a string message and it does the same freeze. No message, no stack trace. Do I have to do something special to get a message. Debugging is gonna be hard if I can't assert! Thanks Francis

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Re: NFS limited to 4K reads/writes
by John Clark 01 Feb '02

01 Feb '02

Am Freitag den, 1. Februar 2002, um 06:53, schrieb Andrew Gallatin: Trust me -- its the NFS read/write size that's killing perf, or at least making a major contribution to it. If I cut the read/write size down to 4k on the FreeBSD host, the read bandwidth drops in half from 50MB/sec to 25MB/sec: Given the details... it sounds like the same limitation that AppleTalk had at 500 byte packets being sent over a 1500 byte ethernet channel... You indicated your packet size on the wire was about 9000 so obviously one could take twice as much data per packet setup time, than the 4K which you indicate NFS seems to be limited at.

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Re: NFS limited to 4K reads/writes
by Andrew Gallatin 01 Feb '02

01 Feb '02

John Clark writes: > > Am Donnerstag den, 31. Januar 2002, um 08:52, schrieb Andrew Gallatin: > > > > > By poor performnace, I mean that Darwin reads at 12MB/sec over a > > 2Gb/sec link. Tru64 and FreeBSD can both read at 50MB/sec. (this is > > from a file warm in the server's cache; no disk I/O). Darwin performs > > just as well as the competition when its the server... > > Since network performance triggers my carnivore monitoring software... I understand.. I should have posted more details. > I'll assume that by '2 Gb/sec' link, one is talking about gigabit > ethernet > in full duplex mode. No, actually. The link is Myrinet-2000 (Full-duplex 2+2 Gb/sec). > How are you measuring your performance. Also what are the hardware > details, for example Darwin on a G4 with the internal gigabit ethernet > interface; Tru65 or FreeBSD on a ???. The mac is a dual g4 800MHz, running 10.1. The PCI bus is capable of roughly 240MB/sec for reads and writes. The FreeBSD host is running FreeBSD 4.5-RELEASE on a dual 1Ghz PIII with a Serverworks LE chipset whose PCI performance is roughly 450MB/sec for reads and 500MB/sec for writes. The alpha is a 500MHz 21264 (a Monet) with a tsunami chipset whose PCI performance is rougly 190MB/sec reads and 240MB/sec writes. The Myrinet device is a a 64-bit/66MHz device (running at 64-bits/33MHz in the Mac and the Alpha) and these are actual, observed performance numbers with the hosts in question. In OS-Bypass mode (no copies DMA to/from wired user buffers, no sockets, no interrupts) the device can sustain 200MB/sec between the FreeBSD host and the mac (unidirectional, symetrical). > Also have you tried ttcp and verified the 50 MB/s is symetrical. More or less. In ethernet emulation mode, I use netperf, and its actually quite a bit better than 50MB/sec.. The following is from using netperf between the mac and the FreeBSD box. The ethernet emulation MTU is 9000 bytes. The mac can send TCP at 670Mb/sec and receive at 750Mb/sec (256K socket buffers). With 8K UDP datagrams, it can send at a hair over 1Gb/sec and receive at 500Mb/sec. Actually ~900Mb/sec makes it into the host and a little less than half are dropped due to full socket buffers. With 4K datagrams, it can send at a hair under 700Mb/sec and receive at a little over 400Mb/sec. These numbers don't change much when I boot the PC into linux 2.4.16 (the tcp send numbers decrease a little, and the receive numbers increase a little, udp stays the same). Trust me -- its the NFS read/write size that's killing perf, or at least making a major contribution to it. If I cut the read/write size down to 4k on the FreeBSD host, the read bandwidth drops in half from 50MB/sec to 25MB/sec: # mount_nfs -U -a 4 -w 16384 -r 16384 g4-my:/private/var/tmp /mnt # dd if=/mnt/zot of=/dev/null bs=64k 2400+0 records in 2400+0 records out 157286400 bytes transferred in 3.145618 secs (50001749 bytes/sec) # umount /mnt # mount_nfs -U -a 4 -w 4096 -r 4096 g4-my:/private/var/tmp /mnt # dd if=/mnt/zot of=/dev/null bs=64k 2400+0 records in 2400+0 records out 157286400 bytes transferred in 6.204624 secs (25349868 bytes/sec) FWIW, the mac has always felt rather slow for NFS even on a 100Mb/s network. (reads at 5MB/sec rather than 10 like FreeBSD & newer versions of linux), so this is something of a problem even on commodity networks. I just never bothered looking into it until I was stress testing my Myrinet driver and noticed how low the bonnie numbers were.. Cheers, Drew

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Re: NFS limited to 4K reads/writes
by John Clark 01 Feb '02

01 Feb '02

Am Donnerstag den, 31. Januar 2002, um 08:52, schrieb Andrew Gallatin: By poor performnace, I mean that Darwin reads at 12MB/sec over a 2Gb/sec link. Tru64 and FreeBSD can both read at 50MB/sec. (this is from a file warm in the server's cache; no disk I/O). Darwin performs just as well as the competition when its the server... Since network performance triggers my carnivore monitoring software... I'll assume that by '2 Gb/sec' link, one is talking about gigabit ethernet in full duplex mode. How are you measuring your performance. Also what are the hardware details, for example Darwin on a G4 with the internal gigabit ethernet interface; Tru65 or FreeBSD on a ???. Also have you tried ttcp and verified the 50 MB/s is symetrical.

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