Linux io_uring VFS backend.

[Jeremy Allison]

On Fri, Feb 07, 2020 at 02:14:06PM +0100, Stefan Metzmacher via samba-technical wrote:
> Hi Jeremy,
> 
> >> Any chance we can get the io_uring VFS
> >> code checked in for 4.12 ?
> >>
> >> Would love to see that as an option
> >> for Linux users.
> >>
> >> I'm happy to review / test !
> > 
> > Look at https://gitlab.com/samba-team/samba/merge_requests/529
> > I just rebased on current master.
> > 
> > The ubuntu 18.04 hwe kernel is up to 5.3 now.
> > But you need the liburing library from https://git.kernel.dk/liburing
> > 
> > I typically use
> >  ./configure --prefix=$HOME/prefix/liburing
> >  make
> >  make install
> > 
> > And for Samba
> > 
> >  PKG_CONFIG_PATH="$HOME/prefix/liburing/lib/pkgconfig/:${PKG_CONFIG_PATH}"
> >  export PKG_CONFIG_PATH
> >  ./configure ...
> > 
> > Note it won't currently work with a 5.4.15 kernel. The regression
> > is revert in 5.5 and most likely backported to 5.4.16.
> > 
> > Please test and it and play with the possible config options.
> > If you can provide some numbers, which show if the options have
> > any impact.
> > 
> > If everything works out ok, I'm happy to push it to master and
> > backport to v4-12-test.
> 
> Ok, I've done some basic testing and I'm able to speed up
> a smbclient 'get largefile /dev/null' against smbd on loopback
> from ~ 2.2GByte/s to 2.7GBytes/s by using the io_uring module.
> 
> I've added at least compile time tests for gitlab
> and removed the WIP status of the merge request.
> 
> Please review and push to master. Once it's in master
> I'm happy to backport it to v4-12-test and write a WHATSNEW entry.

Great ! Thanks. I'll review asap.