On Wed, Jan 29, 2020 at 06:44:05PM +0300, Konstantin Khlebnikov wrote: > Function ext4_update_other_inodes_time() implements optimization which > opportunistically updates times for inodes within same inode table block. > > For now concurrent inode lookup by number does not scale well because > inode hash table is protected with single spinlock. It could become very > hot at concurrent writes to fast nvme when inode cache has enough inodes. > > Probably someday inode hash will become searchable under RCU. > (see linked patchset by David Howells) > > Let's skip concurrent updates instead of wasting cpu time at spinlock. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Link: https://lore.kernel.org/lkml/155620449631.4720.8762546550728087460.stgit@xxxxxxxxxxxxxxxxxxxxxx/ Hmm.... I wonder what Al thinks of adding a varaint of find_inode_nowait() which uses tries to grab the inode_hash_lock() using a trylock, and returns ERR_PTR(-EAGAIN) if the attempt to grab the lock fails. This might be better since it will prevent other conflicts between ext4_update_other_inodes_time() and other attempts to lookup inodes which can't be skipped if things are busy. - Ted
