This patchset cleans up some of the ugly code from my last refactor, and speeds up multipathd path checking, by refactoring how paths are checked. multipathd previously ran the checker on a path, waited briefly for it to complete, and if it did, updated the path and the priorities for the multipath device and possibly reloaded it. This had multiple issues. 1. All the paths waited for their checkers to complete serially. This wasted time with no benefit. It also meant that it wasn't that uncommon for a checker to not finish in time, and get marked pending. 2. The prioritiers could get run on paths multiple times during a checker loop if multiple paths were restored at the same time, which is a common occurance. 3. In an effort to keep a multipath device's state consistent despite the delays introduced by waiting for the path checkers, paths were checked by multipath device. However checking the paths could involve reloading a multipath device table, or even removing a multipath device. This added some ugly backout and retry logic to the path check code. With this patchset, the code now first starts the path checkers on all devices due for a path check. Then it goes back and updates the state of all the path devices, waiting at most a total of 1ms if there are checkers that need waiting for. Once all of the paths have been updated, it goes through each multipath device, updating path priorities and reloading the device as necessary. This allows multipathd to spend less time and do less redundant work while checking paths, while making paths slightly more likely to not spend a checker cycle marked as pending. Since there isn't a delay waiting for the previous checker before starting the next one, the path checker code has reverted to checking all paths in pathvec order, instead of by multipath device. Updating the paths in pathvec order simplifies the code, since the multipath devices can change during path updates. Starting the checkers in pathvec order keeps a path from having its checker started towards the end of the list of paths but checking for the result towards the start of the list of paths. However, it's possible to start the checkers by multipath device without adding much complexity, if people think that the benfit of starting the checkers as close together as possible outweighs the benefit of giving each checker as close to the same amount of time as possible to complete. Benjamin Marzinski (15): libmultipath: store checker_check() result in checker struct libmultipath: add missing checker function prototypes libmultipath: split out the code to wait for pending checkers libmultipath: remove pending wait code from libcheck_check calls multipath-tools tests: fix up directio tests libmultipath: split get_state into two functions libmultipath: change path_offline to path_sysfs_state multipathd: split check_path_state into two functions multipathd: split do_checker_path multipathd: split check_path into two functions multipathd: split handle_uninitialized_path into two functions multipathd: split check_paths into two functions multipathd: update priority once after updating all paths multipathd: remove pointless check multipathd: fix deferred_failback_tick for reload removes libmultipath/checkers.c | 35 +-- libmultipath/checkers.h | 8 +- libmultipath/checkers/directio.c | 129 ++++++---- libmultipath/checkers/tur.c | 66 +++-- libmultipath/discovery.c | 90 ++++--- libmultipath/discovery.h | 6 +- libmultipath/libmultipath.version | 3 +- libmultipath/print.c | 2 +- libmultipath/propsel.c | 1 + libmultipath/structs.h | 21 +- multipathd/main.c | 385 ++++++++++++++++++------------ tests/directio.c | 133 +++++++---- 12 files changed, 546 insertions(+), 333 deletions(-) -- 2.45.0
