On Wed, Mar 23, 2022 at 11:26:11AM +0100, Bernd Schubert wrote: > On 3/23/22 08:16, Greg KH wrote: > > On Tue, Mar 22, 2022 at 08:27:12PM +0100, Miklos Szeredi wrote: > > > Add a new userspace API that allows getting multiple short values in a > > > single syscall. > > > > > > This would be useful for the following reasons: > > > > > > - Calling open/read/close for many small files is inefficient. E.g. on my > > > desktop invoking lsof(1) results in ~60k open + read + close calls under > > > /proc and 90% of those are 128 bytes or less. > > > > As I found out in testing readfile(): > > https://lore.kernel.org/r/20200704140250.423345-1-gregkh@xxxxxxxxxxxxxxxxxxx > > > > microbenchmarks do show a tiny improvement in doing something like this, > > but that's not a real-world application. > > > > Do you have anything real that can use this that shows a speedup? > > Add in network file systems. Demonstrating that this is useful locally and > with micro benchmarks - yeah, helps a bit to make it locally faster. But the > real case is when thousands of clients are handled by a few network servers. > Even reducing wire latency for a single client would make a difference here. I think I tried running readfile on NFS. Didn't see any improvements. But please, try it again. Also note that this proposal isn't for NFS, or any other "real" filesystem :) > There is a bit of chicken-egg problem - it is a bit of work to add to file > systems like NFS (or others that are not the kernel), but the work won't be > made there before there is no syscall for it. To demonstrate it on NFS one > also needs a an official protocol change first. And then applications also > need to support that new syscall first. > I had a hard time explaining weather physicist back in 2009 that it is not a > good idea to have millions of 512B files on Lustre. With recent AI workload > this gets even worse. Can you try using the readfile() patch to see if that helps you all out on Lustre? If so, that's a good reason to consider it. But again, has nothing to do with this getvalues(2) api. thanks, greg k-h
