[Gluster-devel] Adding xxhash to gluster code base

Wed Jun 28 07:32:17 UTC 2017

On Wed, Jun 28, 2017 at 12:51:07PM +0530, Amar Tumballi wrote:
> On Tue, Jun 27, 2017 at 8:46 PM, Niels de Vos <ndevos at redhat.com> wrote:
> 
> > On Tue, Jun 27, 2017 at 08:09:25AM -0400, Kaleb S. KEITHLEY wrote:
> > >
> > > xxhash doesn't seem to change much. Last update to the non-test code was
> > six
> > > months ago.
> > >
> > > bundling giant (for some definition of giant) packages/projects would be
> > > bad. bundling two (three if you count the test) C files doesn't seem too
> > bad
> > > when you consider that there are already three or four packages in fedora
> > > (perl, python, R-digest, ghc (gnu haskell) that have implementations of
> > > xxhash or murmur but didn't bother to package a C implementation and use
> > it.
> >
> > I prefer to have as little maintenance components in the Gluster sources
> > as we can. The maintenance burdon is already very high. The number of
> > changes to xxhash seem limited, but we still need someone to track and
> > pay attention to them.
> >
> 
> I agree that someone should maintain it, and we should add it to
> MAINTAINERS file
> (or some other place, where we are tracking the dependencies).
> 
> For now, Kotresh will be looking into keeping these changes up-to-date with
> upstream xxhash project, along with me.

Kotresh as maintainer/owner, and Aravinda as peer?

> > > I'd be for packaging it in Fedora rather than bundling it in gluster. But
> > > then we get to "carry" it in rhgs as we do with userspace-rcu.
> >
> > We should descide what the most maintainable solution is. Having package
> > maintainers with the explicit task to keep xxhash updated and current is
> > apealing to me. Merging (even small) projects into the Gluster codebase
> > will add more maintenance need to the project members. Therefor I have a
> > strong preference to use xxhash (or an other library) that is provided
> > by distributions. The more common the library is, the better it will be
> > maintained without our (Gluster Community's) help.
> >
> >
> While this is desirable, we didn't see any library available for xxhash (
> http://cyan4973.github.io/xxHash/) in our distro.
> 
> I would recommend taking these patches with TODO to use library in future
> when its available, and continue to have xxhash in 'contrib/'. It is not
> new for us to take code from different libraries and use it for our need
> and maintain only that part (eg. libfuse). Lets treat this as similar setup.

Yes, if there is no suitable alternative available in the majority of
distributions, this is the only sensible approach. Much of the code in
contrib/ is not maintained at all. We should prevent this from happening
with new code and assigning an owner/maintainer and peer(s) just like
for other components is a must.

Thanks,
Niels

> 
> Regards,
> Amar
> 
> 
> 
> 
> 
> > Niels
> >
> >
> > > On 06/27/2017 04:08 AM, Niels de Vos wrote:
> > > > On Tue, Jun 27, 2017 at 12:25:11PM +0530, Kotresh Hiremath Ravishankar
> > wrote:
> > > > > Hi,
> > > > >
> > > > > We were looking for faster non-cryptographic hash to be used for the
> > > > > gfid2path infra [1]
> > > > > The initial testing was done with md5 128bit checksum which was a
> > slow,
> > > > > cryptographic hash
> > > > > and using it makes software not complaint to FIPS [2]
> > > > >
> > > > > On searching online a bit we found out xxhash [3] seems to be faster
> > from
> > > > > the results of
> > > > > benchmark tests shared and lot of projects use it. So we have
> > decided to us
> > > > > xxHash
> > > > > and added following files to gluster code base with the patch [4]
> > > > >
> > > > >      BSD 2-Clause License:
> > > > >         contrib/xxhash/xxhash.c
> > > > >         contrib/xxhash/xxhash.h
> > > > >
> > > > >      GPL v2 License:
> > > > >         tests/utils/xxhsum.c
> > > > >
> > > > > NOTE: We have ignored the code guideline check for these files as
> > > > > maintaining it
> > > > > further becomes difficult.
> > > > >
> > > > > Please comment on the same if there are any issues around it.
> > > >
> > > > How performance critical is the hashing for gfid2path?
> > > >
> > > > What is the plan to keep these files maintained? At minimal we need to
> > > > add these files to MAINTAINERS and the maintainers need to cherry-pick
> > > > updates and bugfixes from the original project. The few patches a year
> > > > makes this a recurring task that should not be forgoten. It would be
> > > > much better to use this as an external library that is provided by the
> > > > distributions. We already rely on OpenSSL, does this library not
> > provide
> > > > an alternative 'FIPS approved' hashing that performs reasonably well?
> > > >
> > > > Some distributions are very strict on bundling external projects, and
> > we
> > > > need to inform the packagers about the additions so that they can
> > handle
> > > > it correctly. Adding an external project to contrib/ should be
> > mentioned
> > > > in the release notes at the very least.
> > > >
> > > > Note that none of the symbols of any public functions in Gluster may
> > > > collide with functions in standard distribution libraries. This causes
> > > > for regular problems with gfapi applications. All exposed symbols that
> > > > get imported in contrib/ should have a gf_ prefix.
> > > >
> > > > Thanks,
> > > > Niels
> > > >
> > > >
> > > > >
> > > > > [1] Issue: https://github.com/gluster/glusterfs/issues/139
> > > > > [2] https://en.wikipedia.org/wiki/Federal_Information_
> > Processing_Standards
> > > > > [3] http://cyan4973.github.io/xxHash/
> > > > > [4] https://review.gluster.org/#/c/17488/10
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Thanks and Regards,
> > > > > Kotresh H R and Aravinda VK
> > >
> >
> 
> 
> 
> -- 
> Amar Tumballi (amarts)