Re: [RFC PATCH 0/5] alternate dmevents waiter method

[Xose Vazquez Perez <xose.vazquez@gmail.com>]

On 02/10/2018 06:07 AM, Benjamin Marzinski wrote:

> This patchset implements a new method of getting dmevents for
> multipathd.
1-4/5 were Reviewed-by: Martin Wilck <mwilck@suse.com>.
And in 5/5, consensus was reached at the end: https://marc.info/?t=151823942200001
but they are t.

status?

> With the existing wait code, multipathd needs to create a waiter thread
> for every multipath device. This can become very wasteful in setups with
> large numbers of multipath devices. These duplicate threads all are
> serialized to update the multipath devices, so they don't actually speed
> up dmevent handling.
> 
> The new method uses the new dmevent polling ability introduced in the
> 4.37.0 device-mapper kernel module.  The original method has been
> retained for backwards compatablility, and it is possible to force
> multipathd to use the orignal method on newer kernels. The benefit of
> this new method is that there is only one thread necessary to wait on
> dmevents, which can be started when device-mapper starts, and stopped
> during shutdown, just like the other main threads.
> 
> These patches use device-mapper features that don't have a libdevmapper
> API.  They will switch over as soon as support is available in
> libdevmapper.
> 
> This patchset is based on top of my recent "[PATCH v2 0/7] multipath:
> miscellaneous bug fixes". It doesn't touch the tur checker, so changes
> to "[PATCH v2 1/7] libmultipath: fix tur checker locking" won't change
> anything in this set.
> 
> Benjamin Marzinski (5):
>   libmultipath: move remove_map waiter code to multipathd
>   move waiter code from libmultipath to multipathd
>   call start_waiter_thread() before setup_multipath()
>   libmultipath: add helper functions
>   multipathd: RFC add new polling dmevents waiter thread
> 
>  libmultipath/Makefile      |   2 +-
>  libmultipath/devmapper.c   |  28 +++-
>  libmultipath/devmapper.h   |   3 +-
>  libmultipath/structs_vec.c | 138 +---------------
>  libmultipath/structs_vec.h |   6 +-
>  libmultipath/vector.c      |  16 +-
>  libmultipath/vector.h      |   1 +
>  libmultipath/waiter.c      | 215 ------------------------
>  libmultipath/waiter.h      |  17 --
>  multipathd/Makefile        |   3 +-
>  multipathd/dmevents.c      | 396 +++++++++++++++++++++++++++++++++++++++++++++
>  multipathd/dmevents.h      |  13 ++
>  multipathd/main.c          | 194 ++++++++++++++++++++--
>  multipathd/waiter.c        | 215 ++++++++++++++++++++++++
>  multipathd/waiter.h        |  17 ++
>  15 files changed, 869 insertions(+), 395 deletions(-)
>  delete mode 100644 libmultipath/waiter.c
>  delete mode 100644 libmultipath/waiter.h
>  create mode 100644 multipathd/dmevents.c
>  create mode 100644 multipathd/dmevents.h
>  create mode 100644 multipathd/waiter.c
>  create mode 100644 multipathd/waiter.h
>