On Wed, 26 Jan 2022 at 02:57, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > On Wed, Jan 26, 2022 at 11:02:16AM +1100, NeilBrown wrote: > > On Wed, 26 Jan 2022, J. Bruce Fields wrote: > > > On Tue, Jan 25, 2022 at 03:15:42PM -0600, Patrick Goetz wrote: > > > > So the directory is locked while the inode is created, or something > > > > like this, which makes sense. > > > > > > It accomplishes a number of things, details in > > > https://www.kernel.org/doc/html/latest/filesystems/directory-locking.html > > > > Just in case anyone is interested, I wrote this a while back: > > > > http://lists.lustre.org/pipermail/lustre-devel-lustre.org/2018-November/008177.html > > > > it includes a patch to allow parallel creates/deletes over NFS (and any > > other filesystem which adds support). > > I doubt it still applies, but it wouldn't be hard to make it work if > > anyone was willing to make a strong case that we would benefit from > > this. Well, I couldn't resist quickly testing Neil's patch. I found it applied okay to v5.6.19 with minimal edits. As before, without the patch, parallel file creates in a single directory with 1000 threads topped out at an aggregate of 3 creates/s over a 200ms link. With the patch it jumps up to 1,200 creates/s. So a pretty dramatic difference. I can't say if there are any other side effects or regressions as I only did this simple test. It's great for our super niche workloads and use case anyway. Daire > Neato. > > Removing the need to hold an exclusive lock on the directory across > server round trips seems compelling to me.... > > I also wonder: why couldn't you fire off the RPC without any locks, then > wait till you get a reply to take locks and update your local cache? > > OK, for one thing, calls and replies and server processing could all get > reordered. We'd need to know what order the server processed operations > in, so we could process replies in the same order. > > --b.
