I just merged a quite invasive patch that needs commenting. The patch explore a new solution to /sbin/multipath inefficiency wrt systems with lots of paths. What did we have : ================== The previous attempt was the cache file plus hot/cold policy, which was suboptimal in many ways : - hard to get the security right - early userspace annoyances wrt umounted FS - needs to allocate a few bytes on FS - the 5 seconds hot to cold policy is not adequate for everyone (see recent Adic post) - hard to settle on an a consensual FS location for the file The proposed solution is : "/sbin/multipath asks the path cache to multipathd through its unix socket" (the same used for the CLI). When the ademon doesn't run, multipath has to do a full rescan. What do we get : ================ - security is easy - no more FS allocation to satisfy - The daemon has its pathvec always up-to-date, thanks to its event-driven model. No more hot/cold policy. What should be debated : ======================== - settle on a FS socket location (currently /var/cache/multipath/uxsock) - people who care about early userspace have now 2 options : - No daemon in early userspace, and disable hotplug-triggered multipath. /sbin/multipath is ran once. - Start the daemon in early userspace, let multipath be hotplug-triggered Comments and critics are welcome. Regards, -- christophe varoqui <christophe.varoqui@xxxxxxx>
