Kip Macy wrote: > I think that for most of us this is the "nuclear reactor" in phk's > bikeshed story :) The Nuclear reactor is from the SVN guys talk on "poisonous personalities in open software projects" I think. where they declared it to be the logically opposite corollary of the Bikeshed. Doug, As a long term developer with a good track record, most of us are just going to say "probably works fine and I have no idea about that stuff" and leave it at that. Who do you think has any idea about this stuff? > > > I had a tested and re-factored tcp_output which got essentially no comments. > > -Kip > > On Fri, Mar 21, 2008 at 3:27 AM, Doug Rabson <dfr_at_rabson.org> wrote: >> As I mentioned previously, I have been working on a brand new NFS Lock >> Manager which runs in kernel mode and uses the normal local locking >> infrastructure for its state. I'm currently trying to tie up the last >> few loose ends before committing this work to current. You can find a >> snapshot of this code at http://people.freebsd.org/~dfr/lockd-RC1-20032008.diff >> . >> >> To try it out, take a recent current (I last merged with current on >> 20th March) and apply the patch. Build a kernel with the NFSLOCKD >> option and add '-k' to 'rpc_lockd_flags' in rc.conf. You will need to >> build and install at least a new libc and rpc.lockd. >> >> At this point, it would be useful to get some extra eyes to look over >> my changes. In particular the following: >> >> 1. Choice of syscall number - I found one spare next to the NFS >> syscall and took that. The new syscall is listed in the FBSD_1.1 >> namespace, possibly it should be somewhere else. >> >> 2. ABI compatibility - I extended the flock structure by one member >> (adding l_sysid). I have added new operations to fcntl to support the >> new extended structure, leaving the old operations in place to work on >> the old structure. The kernel translates old to new and vice versa. No >> attempt is made to allow a new userland to work with an old kernel. >> >> 3. The local lock manager has had a complete rewrite to support >> required features. The new local lock manager supports a more flexible >> model of lock ownership (which can support remote lock owners). I have >> replaced the inadequate deadlock detection code with a new (and fast) >> graph based system. Using the deadlock graph, I was able to avoid the >> 'thundering herd' issues the old lock code had when many processes >> were contending for the same locked region. Given the extent of the >> changes, wider testing and review would be extremely welcome. >> >> 4. The NFS lock manager itself is brand new code and as such ought to >> be reviewed. I have also ported the userland sunrpc code to run in the >> kernel environment which may prove useful in future. >> >> Highlights include: >> >> * Thread-safe kernel RPC client - many threads can use the same RPC >> client handle safely with replies being de-multiplexed at the socket >> upcall (typically driven directly by the NIC interrupt) and handed off >> to whichever thread matches the reply. For UDP sockets, many RPC >> clients can share the same socket. This allows the use of a single >> privileged UDP port number to talk to an arbitrary number of remote >> hosts. >> >> * Single-threaded kernel RPC server. Adding support for multi-threaded >> server would be relatively straightforward and would follow >> approximately the Solaris KPI. A single thread should be sufficient >> for the NLM since it should rarely block in normal operation. >> >> * Kernel mode NLM server supporting cancel requests and granted >> callbacks. I've tested the NLM server reasonably extensively - it >> passes both my own tests and the NFS Connectathon locking tests >> running on Solaris, Mac OS X and Ubuntu Linux. >> >> * Userland NLM client supported. While the NLM server doesn't have >> support for the local NFS client's locking needs, it does have to >> field async replies and granted callbacks from remote NLMs that the >> local client has contacted. We relay these replies to the userland >> rpc.lockd over a local domain RPC socket. >> >> * IPv6 should be supported but has not been tested since I've been >> unable to get IPv6 to work properly with the Parallels virtual >> machines that I've been using for development. >> >> * Robust deadlock detection for the local lock manager. In particular >> it will detect deadlocks caused by a lock request that covers more >> than one blocking request. As required by the NLM protocol, all >> deadlock detection happens synchronously - a user is guaranteed that >> if a lock request isn't rejected immediately, the lock will eventually >> be granted. The old system allowed for a 'deferred deadlock' condition >> where a blocked lock request could wake up and find that some other >> deadlock-causing lock owner had beaten them to the lock. >> >> * Since both local and remote locks are managed by the same kernel >> locking code, local and remote processes can safely use file locks for >> mutual exclusion. Local processes have no fairness advantage compared >> to remote processes when contending to lock a region that has just >> been unlocked - the local lock manager enforces a strict first-come >> first-served model for both local and remote lockers. > _______________________________________________ > freebsd-current_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"Received on Fri Mar 21 2008 - 18:07:45 UTC
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