On Fri, May 15, 2015 at 03:15:48PM -0600, Andreas Dilger wrote: > On May 14, 2015, at 5:23 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > > > > On Wed, May 13, 2015 at 08:52:59PM -0700, Linus Torvalds wrote: > >> On Wed, May 13, 2015 at 8:30 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > >>> > >>> Maybe... I'd like to see the profiles, TBH - especially getxattr() and > >>> access() frequency on various loads. Sure, make(1) and cc(1) really care > >>> about stat() very much, but I wouldn't be surprised if something like > >>> httpd or samba would be hitting getxattr() a lot... > >> > >> So I haven't seen samba profiles in ages, but iirc we have more > >> serious problems than trying to speed up basic filename lookup. > >> > >> At least long long ago, inode semaphore contention was a big deal, > >> largely due to readdir(). > > > > It still is - it's the prime reason people still need to create > > hashed directory structures so that they can get concurrency in > > directory operations. IMO, concurrency in directory operations is a > > more important problem to solve than worrying about readdir speed; > > in large filesystems readdir and lookup are IO bound operations and > > so everything serialises on the IO as it's done with the i_mutex > > held.... > > We've had a patch[*] to add ext4 parallel directory operations in Lustre for > a few years, that adds separate locks for each internal tree and leaf block > instead of using i_mutex, so it scales as the size of the directory grows. > This definitely improved many-threaded directory create/lookup/unlink > performance (rename still uses a single lock). Yup, we can do the same to XFS to implement concurrent modifications. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
