On Wed, 22 May 2024 at 01:12, kernel test robot <oliver.sang@xxxxxxxxx> wrote: > > kernel test robot noticed a 6.7% improvement of stress-ng.touch.ops_per_sec on: > > commit: 3681ce364442ce2ec7c7fbe90ad0aca651db475b ("[PATCH] vfs: Delete the associated dentry when deleting a file") Ok, since everything else is at least tentatively in the noise, and the only hard numbers we have are the ones from Yafang's Elasticsearch load and this - both of which say that this is a good patch - I decided to just apply this ASAP just to get more testing. I just wanted to note very explicitly that this is very much tentative: this will be reverted very aggressively if somebody reports some other real-world load performance issues, and we'll have to look at other solutions. But I just don't think we'll get much more actual testing of this without just saying "let's try it". Also, I ended up removing the part of the patch that stopped clearing the DCACHE_CANT_MOUNT bit. I think it's right, but it's really unrelated to the actual problem at hand, and there are other cleanups - like the unnecessary dget/dput pair - in this path that could also be looked at. Anyway, let's see if somebody notices any issues with this. And I think we should look at the "shrink dentries" case anyway for other reasons, since it's easy to create a ton of negative dentries with just lots of lookups (rather than lots of unlinking of existing files). Of course, if you do billions of lookups of different files that do not exist in the same directory, I suspect you just have yourself to blame, so the "lots of negative lookups" load doesn't sound particularly realistic. TLDR; I applied it for testing because we're in the merge window and there's no reason not to try. Linus