On Sat, 4 Feb 2023, Trond Myklebust wrote: > > On Feb 3, 2023, at 18:53, Hugh Dickins <hughd@xxxxxxxxxx> wrote: > > On Fri, 3 Feb 2023, Chuck Lever III wrote: > >>> On Feb 3, 2023, at 5:26 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > >>> The bottom line is that you’ve always been playing the lottery when mounting tmpfs over NFS. > >> > >> I'm not debating the truth of that. I just don't think we should > >> be making that situation needlessly worse. > >> > >> And I would be much more comfortable with this if it appeared in > >> a man page or on our wiki, or ... I'm sorry, but "some email in > >> 2001" is not documentation a user should be expected to find. > > > > I very much agree with you, Chuck. Making something imperfect > > significantly worse is called "a regression". > > > > And I would expect the (laudable) optimization which introduced > > that regression to be reverted from 6.2 for now, unless (I imagine > > not, but have no clue) it can be easily conditionalized somehow on > > not-tmpfs or not-simple_dir_operations. But that's not my call. > > > > What is the likelihood that simple_dir_operations will be enhanced, > > or a satisfactory complicated_dir_operations added? I can assure > > you, never by me! If Al or Amir or some dcache-savvy FS folk have > > time on their hands and an urge to add what's wanted, great: but > > that surely will not come in 6.2, if ever. > > > > More likely that effort would have to come from the NFS(D) end, > > who will see the benefit. And if there's some little tweak to be > > made to simple_dir_operations, which will give you the hint you need > > to handle it better, I expect fsdevel would welcome a patch or two. > > > > Hugh > > > No! If it was impossible to hit this problem before the patch, then I might agree with you. However what it does is exposes a problem that has always existed, but was a lot less likely to happen timing wise when we were allowing glibc to suck in all 50000 or so directory entries in one gulp. > > IOW: this patch doesn’t cause the problem, it just makes it easier to hit when you are using a high performance setup like Chuck's. It was always easy to hit when you were using slower networking and/or smaller rsize values against a remote server with multiple clients creating + deleting files in the same NFS exported tmpfs directory. > _________________________________ > Trond Myklebust > Linux NFS client maintainer, Hammerspace > trond.myklebust@xxxxxxxxxxxxxxx I can only repeat, making something imperfect significantly worse is called "a regression". Hugh
