I like to add some info on a thread from 2015: I recently worked on my file search tool (FAF) and wanted to make sure that I use the best method to deep-scan directory contents.
I had expected that getattrlistbulk() would always be the best choice, but it turns out that opendir/readdir perform much better in some cases, oddly (this is about reading just the file names, no other attributes). See my blog post: https://blog.tempel.org/2019/04/dir-read-performance.html <https://blog.tempel.org/2019/04/dir-read-performance.html> There's also a test project trying out the various methods. Any comments, insights, clarifications and bug reports are most welcome. Enjoy, Thomas Tempelmann > On 12. Jan 2015, at 17:33, Jim Luther <luthe...@apple.com> wrote: > > getattrlistbulk() works on all file systems. If the file system supports bulk > enumeration natively, great! If it does not, then the kernel code takes care > of it. In addition, getattrlistbulk() supports all non-volume attributes > (getattrlistbulk only supported a large subset). > > The API calling convention for getattrlistbulk() is slightly different than > getattrlistbulk() — read the man page carefully. In particular: > > • ATTR_CMN_NAME and ATTR_CMN_RETURNED_ATTRS are required (requiring > ATTR_CMN_NAME allowed us to get rid of the newState argument). > • A new attribute, ATTR_CMN_ERROR, can be requested to detect error > conditions for a specific directory entry. > • The method for determining when enumeration is complete is different. You > just keep calling getattrlistbulk() until 0 entries are returned. > > - Jim > >> On Jan 11, 2015, at 9:31 PM, James Bucanek <subscri...@gloaming.com> wrote: >> >> Eric, >> >> I would just like to clarify: the new getattrlistbulk() function works on >> all filesystem. We don't have to check the volume's VOL_CAP_INT_READDIRATTR >> capability before calling it, correct? >> >> James Bucanek >> >>> Eric Tamura December 10, 2014 at 5:57 PM >>> It should be much faster. >>> >>> Also note that as of Yosemite, we have added a new API: getattrlistbulk(2), >>> which is like getdirentriesattr(), but supported in VFS for all >>> filesystems. getdirentriesattr() is now deprecated. >>> >>> The main advantage of the bulk call is that we can return results in most >>> cases without having to create a vnode in-kernel, which saves on I/O: HFS+ >>> on-disk layout is such that all of the directory entries in a given >>> directory are clustered together and we can get multiple directory entries >>> from the same cached on-disk blocks.
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