Re: BSD XFS Port BSD VFS Rewrite
On Wed, Aug 18, 1999 at 08:43:14PM +, Terry Lambert wrote: Nope. The problem is that while stacking (null, umap, and overlay fs's) work, we don't have the coherency issues worked out so that upper layers can cache data. i.e. so that the lower fs knows it has to ask the uper layers to give pages back. :-) But multiple ls -lR's work fine. :-) With UVM in NetBSD, this is (supposedly) not an issue. UBC. UVM is a new memory manager. UBC unifies the buffer cache with the VM system. I was under the impression that th "U" in "UVM" was for "Unified". Does NetBSD not have a unified VM and buffer cache? is th "U" in "UVM" referring not to buffer cache unification, but to platform unification? It was my understanding from John Dyson, who had to work on NetBSD for NCI, that the new NetBSD stuff actually unified the VM and the buffer cache. If this isn't the case, then, yes, you will need to lock all the way up and down, and eat the copy overhead for the concurrency for the intermediate vnodes. 8-(. netbsd w/UVM currently doesn't have unified caches. that feature is what I named UBC, for "unified buffer cache" (ala DEC's UBC). the U in UVM doesn't actually stand for anything. :-) You could actually think of it this way, as well: only FS's that contain vnodes that provide backing should implement VOP_GETPAGES and VOP_PUTPAGES, and all I/O should be done through paging. Right. That's part of UBC. :-) Yep. Again, if NetBSD doesn't have this, it's really important that it obtain it. 8-(. I'm workin' on it... it'll go in soon after the branch for the next release is created (ie. it won't be in the next release, but the one after that). -Chuck To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
Re: BSD XFS Port BSD VFS Rewrite
On Wed, Aug 18, 1999 at 08:43:14PM +, Terry Lambert wrote: Nope. The problem is that while stacking (null, umap, and overlay fs's) work, we don't have the coherency issues worked out so that upper layers can cache data. i.e. so that the lower fs knows it has to ask the uper layers to give pages back. :-) But multiple ls -lR's work fine. :-) With UVM in NetBSD, this is (supposedly) not an issue. UBC. UVM is a new memory manager. UBC unifies the buffer cache with the VM system. I was under the impression that th U in UVM was for Unified. Does NetBSD not have a unified VM and buffer cache? is th U in UVM referring not to buffer cache unification, but to platform unification? It was my understanding from John Dyson, who had to work on NetBSD for NCI, that the new NetBSD stuff actually unified the VM and the buffer cache. If this isn't the case, then, yes, you will need to lock all the way up and down, and eat the copy overhead for the concurrency for the intermediate vnodes. 8-(. netbsd w/UVM currently doesn't have unified caches. that feature is what I named UBC, for unified buffer cache (ala DEC's UBC). the U in UVM doesn't actually stand for anything. :-) You could actually think of it this way, as well: only FS's that contain vnodes that provide backing should implement VOP_GETPAGES and VOP_PUTPAGES, and all I/O should be done through paging. Right. That's part of UBC. :-) Yep. Again, if NetBSD doesn't have this, it's really important that it obtain it. 8-(. I'm workin' on it... it'll go in soon after the branch for the next release is created (ie. it won't be in the next release, but the one after that). -Chuck To Unsubscribe: send mail to majord...@freebsd.org with unsubscribe freebsd-hackers in the body of the message
