On Sun, Jul 31, 2011 at 2:23 AM, Jean-Yves Migeon <jeanyves.mig...@free.fr> wrote: > On 30.07.2011 19:01, Christos Zoulas wrote: >> Module Name: src >> Committed By: christos >> Date: Sat Jul 30 17:01:05 UTC 2011 >> >> Modified Files: >> src/sys/conf: files >> src/sys/kern: init_main.c kern_lwp.c kern_synch.c >> Added Files: >> src/sys/kern: subr_pserialize.c >> src/sys/sys: pserialize.h >> >> Log Message: >> Add an implementation of passive serialization as described in expired >> US patent 4809168. This is a reader / writer synchronization mechanism, >> designed for lock-less read operations. > > Interesting! What would be the direct consumers of such an > implementation? For example, can pserialize be a drop-in replacement for > everything that is rwlock(9) based, or are they limitations?
I plan to use this to protect the vm_physseg array. [1] It is looked up thousands of times in every seconds (on busy systems), performance critical, and very rarely updated (e.g. once a month when a new device is attached/detached). Avoiding atomic ops in such a situation is desirable. Masao [1] http://mail-index.netbsd.org/tech-kern/2010/02/08/msg007262.html > (I am aware that passive serialization is not equivalent to RCU). > > I remember reading articles mentioning how "wonderful" lockless > algorithms are, except in situation where the additional bus > locking/atomic ops involved did not really improve the situation in > highly concurrent systems (and could even make it worse). > > -- > Jean-Yves Migeon > jeanyves.mig...@free.fr >
