>Given the performance bottleneck imposed by sniffing, I suggest that it >is not used anymore in directory listing routines. It should be used >when the user tries to open an unknown file. Let's imagine this case: I don't think this is a good way of thinking about things. The questions are: 1. Is sniffing a good idea? 2. If so does it work correctly? 3. If (1) and (2), is it performing fast enough? I think others have argued persuasively that sniffing is a good idea since unix doesn't generally give file name suffixes to files (even though gnome does), and often files have incorrect suffixes. A number of people have said that there are instances where sniffing is not correctly determining the file type. If true, this is an excellent argument for fixing those cases, but not at all an argument for throwing away sniffing altogether. >From your benchmarking it is clear that (3) is a problem, and sniffing is taking too long. This is not an argument for getting rid of it though, just an argument for speeding it up. Someone suggested running it through a profiler, but I doubt that will be worthwhile--the problem is almost certainly the multiple disk accesses (your disk is having to seek for each file). As others have pointed out, a two pass technique. based on extension and then sniffing is also a bad idea since icons, etc would change in the case of a discrepancy. Sniffing is slow because it opens every file and reads some of it every time you open a given directory. If you want to make this fast, cache filetypes; now opening the huge mp3 folder is just a matter of reading a single cache file and sniffing those files with a modification time later than that of the cache file. Naturally this would only need to be done for those really huge directories, it would probably be a waste for directories with only a hundred files or fewer. I don't think we need to worry about which approach is ultimately going to perform faster. For a program like Nautilus either there is or is not a human-noticeable lag time; improving performance when there is no lag time is totally pointless. A number of people have used Windows as an example of why we don't need to sniff files; though there are a number of features in Windows worth copying this is definitely not one of them. I have worked on some commercial software and the number one frivolous bug report or unfixable user issue occurs when the user attempts to open a file that has an incorrect filename extension. People on this list have suggested that this is a user problem not a software problem (i.e. that the user was stupid and beyond help), but I can assure you that however obvious the connection between the hidden Windows filename extension and the error message that our program gave is to me and you, it was not obvious to a large number of otherwise very intelligent people who just weren't as knowledgeable about computers. People always think that the icon for a file is somehow part of the file (it makes sense if you don't think about it too hard), and so if a file has, say, a jpeg icon it doesn't occur to them that it is not a jpeg. -Jay _______________________________________________ gnome-list mailing list gnome-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gnome-list
