very strange reaction of the md disks

The Ghost the-ghost at
Tue Jun 3 07:44:49 UTC 2008


Maybe I just don't understand something, but anyway, it looks really odd.

I have a machine with 2 Gb RAM with a clean newly-installed FREEBSD-7.0-RELEASE. I make two 300-MB mdconfig disks and populate them, and when the first one was already full and the second one is only half-full, I get a kernel panic "not enough memory". I wonder where did 1,5 Gb go?? Well, I tried to reboot and allocate them with -o reserve to prevent the kernel panic, but the second one said that enough memory can't be allocated (though top still showed 1,5 Gb left). Well, I rebooted and tried to allocate one 1-Gb disk, but it also failed. Then I gave up on this and came to my other work, but when I loaded some small kernel module, I got a kernel panic!! What, didn't the disk allocation have to kinda free up the used memory when it fails?! And then the last thing. I reboot and copy a 220-m file from a samba-mounted directory to my hard drive (UFS2 with soft-updates). I was very surprised to see that one gigabyte of my memory suddenly became used up. I wonder if the soft-updat
 es really don't care about how much memory they use...

A friend of mine told me that such a panic is really a thing to write a bugreport on it, but I know about this behaviour for few years already and so I guess I just don't know something about the memory allocation system, and, kinda, it really works just like that. Should I read something to understand why it's just like that or really write a report on some of these things?..

                                           The Ghost <the-ghost at>

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