December 2003 - Darwin-kernel

Re: virtual memory
by Quinn 02 Dec '03

02 Dec '03

At 1:25 -0800 2/12/03, Steve Dekorte wrote: What's the limit on the amount of virtual memory OSX can support? There's no single answer to this question. Within any normal user task, Mac OS X supports 4 GB of VM. By default, chunks of this address space will be allocated to other things (like the frameworks), so the limit to how much VM you can /allocate/ is less. Within the kernel task, Mac OS X 10.3 supports 3 GB of address space (some of which may be pageable). On earlier systems, this limit was 1 GB. If you consider the totality of all the VM in all the tasks on the system, AFAIK there is no fixed limit. There are a variety of limits that you can run in to, the most likely being disk space. Swap space is allocated from files on the root volume. [Search "/etc/rc" for "dynamic_pager" to see where this is done.] If the root volume fills up, the pager stops paging out and you eventually run so short of physical memory that the system grinds to a halt. S+E -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Technical Support * Networking, Communications, Hardware _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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virtual memory
by Steve Dekorte 02 Dec '03

02 Dec '03

What's the limit on the amount of virtual memory OSX can support? -- Steve _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: mach_task_self()
by Quinn 02 Dec '03

02 Dec '03

At 13:16 -0700 1/12/03, Matt Jaffa wrote: I want the task of the KEXT im writing to be put in that position. Depending on the context in which your KEXT is running, accessing the current task may not make sense. On 26 Sep 2003 Jim Magee posted a long article about this under the subject "MIG RPC from kext question". You should read this (it should be in the list archives) before continuing. The following page has a link to the list archives. <http://www.lists.apple.com/darwin-kernel> S+E -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Technical Support * Networking, Communications, Hardware _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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API reference
by Jeff Nathan 02 Dec '03

02 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Ahh... silly me. The API reference Apple is referring to are the man pages in xnu-xxx/osfmk/man False alarm. (That Apple web page could use some clarification). - -Jeff - -- The original EZ-bake packet oven. http://nemesis.sourceforge.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (Darwin) iD8DBQE/y+NhEqr8+Gkj0/0RAp/SAKC18WJQHoQzIRw2UzBSGXeS5h+SkwCffno6 /zMtGjwe7J3bgp/19vOCBiM= =yBZL -----END PGP SIGNATURE----- _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: mach_task_self()
by Jeff Nathan 02 Dec '03

02 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I've *never* used semaphores in-kernel. I looked around and the apple documentation (which I'll bet you're more familiar with than I am) suggests current_task() should be used to obtain the task_t for semaphore_create(). The Apple documentation in question is here: http://developer.apple.com/documentation/Darwin/Conceptual/ KernelProgramming/synchronization/chapter_15_section_2.html I haven't yet found the MACH API reference that Apple refers to on their website. XCode doesn't seem to know much about this either. Do any of you know where to actually find the MACH API reference Apple refers to on several of their website here: http://developer.apple.com/documentation/Darwin/Conceptual/ KernelProgramming/About/chapter_1_section_5.html#//apple_ref/doc/uid/ TP30000905-CH204-CHDHDDGC (My xnu-517 sources do not contain an API reference) - -Jeff On Dec 1, 2003, at 3:16 PM, Matt Jaffa wrote: Hi, I am trying to use semaphores within the KERNEL, the normal sem_init, etc. I have discovered have been disabled from being able to use inside the KERNEL, So I am looking at the semaphore_create(.......) that can work within the kernel, but it is asking for a task_t task. Now how do i get that, mach_task_self() doesn't work inside the kernel either. I want the task of the KEXT im writing to be put in that position. Any ideas? Thanks _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored. - -- Craft custom packets from the comfort of your home. http://nemesis.sourceforge.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (Darwin) iD8DBQE/y+I+Eqr8+Gkj0/0RAs5EAJ48wACJHMHHB4u6evrXXHWB8sH0YQCfQ74z AYXBomVyDCAeYc3cssXBxeM= =ZY2k -----END PGP SIGNATURE----- _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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mach_task_self()
by Matt Jaffa 01 Dec '03

01 Dec '03

Hi, I am trying to use semaphores within the KERNEL, the normal sem_init, etc. I have discovered have been disabled from being able to use inside the KERNEL, So I am looking at the semaphore_create(.......) that can work within the kernel, but it is asking for a task_t task. Now how do i get that, mach_task_self() doesn't work inside the kernel either. I want the task of the KEXT im writing to be put in that position. Any ideas? Thanks _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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Re: fsck vs. Journaled HFS+
by Quinn 01 Dec '03

01 Dec '03

At 16:01 -0700 23/11/03, James Bucanek wrote: I'm trying to find some definitive word about using fsck on a Journaled HFS+ file system. I'm technical editor for a book on OS X and I'd like to get to the bottom of this. I forwarded your questions to the guy who implemented journaling in HFS Plus and he just got back to me with a response... ---------------------------------------------------------------------- What I'm trying to find out is: When do journaling fixes get applied. HFS Plus will replay the journal on an HFS Plus file system at mount time if the last person to touch the file system was a journaling aware system. HFS Plus determines if the last person to touch the file system was journaling aware by looking at the lastMountedVersion field in the volume header. If it is set to 'HFSJ' then we'll replay the journal. Otherwise the journal is discarded because it means either the file system was modified by someone who did not know about journaling or it is clean. Jaguar 10.2.3 and above versions of fsck_hfs will not modify a journaling file system unless given the "-f" option. If you specify "-f" to fsck_hfs it will do its normal business (which as a result sets the lastMountedVersion to 'fsck' so the journal will be discarded at mount time). What exactly does 'fsck -f' do? Under what circumstances can the two conflict? If you have a dirty journaled volume (i.e. one that was hot-unplugged or from a system that lost power or panic'ed) and you were to run "fsck_hfs -f" on it, then fsck_hfs will try to do it job which will most likely fail. This will also cause the journal to get discarded and thus you're likely to get a corrupted disk. A journaled disk with a dirty journal is typically in a state that fsck_hfs can not fix. The best thing you can do is let journaling do its job if a volume is dirty. Just mount it and everything will be fine. Now, having said that there's still the potential that a volume can get corrupted due to bugs in HFS Plus. That is, a bug in HFS Plus (or elsewhere in the kernel) could cause a data structure to be written that is damaged -- journal won't protect against that. The journal just faithfully replays what it is asked to -- if there's something damaged in the data structures, the journal can't know that. So if you suspect that your disk has problems, it is best to unmount it cleanly and run "fsck_hfs -f -n" (or choose "Verify Disk" in Disk Utility) and see if there are any complaints. If there are problems then it is useful to run "fsck_hfs -f -y" or choose "Repair Disk" in Disk Utility to fix the problems. In these cases fsck_hfs can usually fix the problems. It's also a good idea to re-run "fsck_hfs -f -n" afterwards to verify that all the problems are fixed. ---------------------------------------------------------------------- S+E -- Quinn "The Eskimo!" <http://www.apple.com/developer/> Apple Developer Technical Support * Networking, Communications, Hardware _______________________________________________ darwin-kernel mailing list | darwin-kernel(a)lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.

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