On Wed, Mar 23, 2022 at 01:06:33PM +0100, Bernd Schubert wrote: > > > On 3/23/22 12:42, Greg KH wrote: > > 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 :) > > How did you run it on NFS? To get real benefit you would need to add a > READ_FILE rpc to the NFS protocol and code? Just having it locally won't > avoid the expensive wire calls? I did not touch anything related to NFS code, which is perhaps why I did not notice any difference :) thanks, greg k-h
