Why does the data need to be stored with the file (not that it isn't a sensible goal). Why not have a database of files and their usage be maintained by your logic that watches open/close. This would be better at supporting your predictive pre-fetching if the database was designed to allow for the types of searches you need to do. Having to grok the file system for usage information could be slow because it is not tuned for it. Basically you could do this by having a file system "filter" that you could lay over _any_ file system. This filter would maintain the database of usage directly. Basically the moment you try to store this information in the file system you become file system dependent (which may be fine in your solution). -Shawn On Wednesday, March 6, 2002, at 08:56 PM, Ian Brown wrote: I am trying to store statistical information with files that persists across reboots. Theoretically it looks like an attribute record (HFSPlusAttrInlineData) would be the best place to put this information, however it does not look like those work yet (correct me if I am wrong.) FIRST: I want to store a counter with each file (or file metadata) counting open()'s. I can then set them to zero and run filesystem benchmarks and get file access statistics. "But," they say, "this can be done by taking a trace." I know, but it would not show me how to store statistical information with files. Why do I want to do this then? NEXT: I will be able to store predictive information with files. Specifically I would like to store a reference to the file that gets accessed next. I plan to do this at the time of the next open(). This will give me file grouping information and predictive pre-fetching information. The situation with mmap() had not crossed my mind, however I am not sure if it is an issue with what I am ultimately trying to do. Ian What exactly are you trying to do? Is this total number of open() calls for a file counter? Does it persist across reboot? Are you planning on decrementing the counter when close() is called? If so, What do you intend to do for the case open() mmap() close() Now you counter goes to 0, but the inode is still in use... --Umesh -- Umesh Vaishampayan Apple Computer, Inc. Mac OS X Kernel Ph: (408) 974 0229 _______________________________________________ darwin-kernel mailing list | darwin-kernel@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. _______________________________________________ darwin-kernel mailing list | darwin-kernel@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.