4 ms·

I'm not sure about the downvotes, but: "One does not simply own/maintain a new filesystem". Also, I wonder how much of HAMMER2 is tailored towards the DF-BSD

I'm not sure about the downvotes, but: "One does not simply own/maintain a new filesystem". Also, I wonder how much of HAMMER2 is tailored towards the DF-BSD kernel?

tiffanyh 3y ago
> I wonder how much of HAMMER2 is tailored towards the DF-BSD kernel? Given that the same developer is porting HAMMER2 to not only OpenBSD, but also NetBSD and FreeBSD - not much. https://github.com/kusumi https://github.com/kusumi
- sillywalk 3y ago
  This deals with the 'original' Hammer, this is way above my head, and I don't know how much applies to either OS or the HAMMER2 so this is just me posting another link but: "There are several major differences: * All VOP operations related to the namecache... those using named path elements like lookup, rename, etc... those are completely different. The biggest one is that our VOP_NRESOLVE() API is completely different from the old VOP_LOOKUP() API. The old VOP_LOOKUP() API had to handle numerous side effects and I don't recall the FreeBSD namecache subsystem doing any namespace locking (beyond locking vnodes, that is). Also our VOP_NREMOVE() is fairly radically different... it's an all in one call whereas the older VOP_REMOVE was paired with a VOP_LOOKUP that stored side-effects (not sure if FreeBSD has cleaned that up yet). i.e. old was LOOKUP(save side effects) + REMOVE(use side effects). And DragonFly's is just NREMOVE(). * HAMMER uses a far more sophisticated buffer cache call-back interface which allows HAMMER to veto write requests from the buf_daemon's (to enforce certain write ordering requirements). * DragonFly uses a locking model that I don't think FreeBSD has an API for (our token locking model which releases held locks within the model when a thread switches out and reacquires them when the thread switches back in). If FreeBSD also has an API for this model this would be easy to port (if not for all of the above issues). * DragonFly uses a slightly different stacked BUF/BIO mechanic for I/O. This would be easy to port (if not for all of the above issues). * DragonFly's BUF/BIO allows for different buffer sizes within the file buffers (not just the device buffers). Generally speaking there can be significant mixing of buffer sizes and the cluster code has to be able to deal with it given appropriate argumetns. I don't think FreeBSD's cluster code could handle it. Personally I think it might be too much for a GSOC project. -Matt" https://wiki.freebsd.org/PortingHAMMERFS https://wiki.freebsd.org/PortingHAMMERFS

I'm not sure about the downvotes, but: "One does not simply own/maintain a new filesystem". Also, I wonder how much of HAMMER2 is tailored towards the DF-BSD kernel?

tiffanyh 3y ago

> I wonder how much of HAMMER2 is tailored towards the DF-BSD kernel? Given that the same developer is porting HAMMER2 to not only OpenBSD, but also NetBSD and FreeBSD - not much. https://github.com/kusumi https://github.com/kusumi

sillywalk 3y ago
This deals with the 'original' Hammer, this is way above my head, and I don't know how much applies to either OS or the HAMMER2 so this is just me posting another link but: "There are several major differences: * All VOP operations related to the namecache... those using named path elements like lookup, rename, etc... those are completely different. The biggest one is that our VOP_NRESOLVE() API is completely different from the old VOP_LOOKUP() API. The old VOP_LOOKUP() API had to handle numerous side effects and I don't recall the FreeBSD namecache subsystem doing any namespace locking (beyond locking vnodes, that is). Also our VOP_NREMOVE() is fairly radically different... it's an all in one call whereas the older VOP_REMOVE was paired with a VOP_LOOKUP that stored side-effects (not sure if FreeBSD has cleaned that up yet). i.e. old was LOOKUP(save side effects) + REMOVE(use side effects). And DragonFly's is just NREMOVE(). * HAMMER uses a far more sophisticated buffer cache call-back interface which allows HAMMER to veto write requests from the buf_daemon's (to enforce certain write ordering requirements). * DragonFly uses a locking model that I don't think FreeBSD has an API for (our token locking model which releases held locks within the model when a thread switches out and reacquires them when the thread switches back in). If FreeBSD also has an API for this model this would be easy to port (if not for all of the above issues). * DragonFly uses a slightly different stacked BUF/BIO mechanic for I/O. This would be easy to port (if not for all of the above issues). * DragonFly's BUF/BIO allows for different buffer sizes within the file buffers (not just the device buffers). Generally speaking there can be significant mixing of buffer sizes and the cluster code has to be able to deal with it given appropriate argumetns. I don't think FreeBSD's cluster code could handle it. Personally I think it might be too much for a GSOC project. -Matt" https://wiki.freebsd.org/PortingHAMMERFS https://wiki.freebsd.org/PortingHAMMERFS