Messages in this thread | | | Date | Mon, 28 Aug 2006 21:46:11 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH 3/4] RCU: preemptible RCU implementation |
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On Mon, Aug 28, 2006 at 09:42:22PM +0530, Dipankar Sarma wrote: > From: Paul McKenney <paulmck@us.ibm.com> > > This patch implements a new version of RCU which allows its read-side > critical sections to be preempted. It uses a set of counter pairs > to keep track of the read-side critical sections and flips them > when all tasks exit read-side critical section. The details > of this implementation can be found in this paper - > > http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf > > This patch was developed as a part of the -rt kernel > development and meant to provide better latencies when > read-side critical sections of RCU don't disable preemption. > As a consequence of keeping track of RCU readers, the readers > have a slight overhead (optimizations in the paper). > This implementation co-exists with the "classic" RCU > implementations and can be switched to at compiler.
NACK. While a readers can sleep rcu version definitly has it's we should make it all or nothing. Either we always gurantee that a rcu reader can sleep or never without external patches. Having this a config option is the ultimate defeat for any kind of bug reproducabilility.
Please make the patch undconditional and see if it doesn't cause any significant slowdowns in production-like scenaries and then we can switch over to the readers can sleep variant unconditionally at some point.
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