On Wed, Dec 09, 2020 at 12:24:32PM -0800, Saravana Kannan wrote: > On Wed, Dec 9, 2020 at 10:15 AM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, Nov 20, 2020 at 06:02:15PM -0800, Saravana Kannan wrote: > > > The current implementation of fw_devlink is very inefficient because it > > > tries to get away without creating fwnode links in the name of saving > > > memory usage. Past attempts to optimize runtime at the cost of memory > > > usage were blocked with request for data showing that the optimization > > > made significant improvement for real world scenarios. > > > > > > We have those scenarios now. There have been several reports of boot > > > time increase in the order of seconds in this thread [1]. Several OEMs > > > and SoC manufacturers have also privately reported significant > > > (350-400ms) increase in boot time due to all the parsing done by > > > fw_devlink. > > > > > > So this patch series refactors fw_devlink to be more efficient. The key > > > difference now is the addition of support for fwnode links -- just a few > > > simple APIs. This also allows most of the code to be moved out of > > > firmware specific (DT mostly) code into driver core. > > > > > > This brings the following benefits: > > > - Instead of parsing the device tree multiple times (complexity was > > > close to O(N^3) where N in the number of properties) during bootup, > > > fw_devlink parses each fwnode node/property only once and creates > > > fwnode links. The rest of the fw_devlink code then just looks at these > > > fwnode links to do rest of the work. > > > > > > - Makes it much easier to debug probe issue due to fw_devlink in the > > > future. fw_devlink=on blocks the probing of devices if they depend on > > > a device that hasn't been added yet. With this refactor, it'll be very > > > easy to tell what that device is because we now have a reference to > > > the fwnode of the device. > > > > > > - Much easier to add fw_devlink support to ACPI and other firmware > > > types. A refactor to move the common bits from DT specific code to > > > driver core was in my TODO list as a prerequisite to adding ACPI > > > support to fw_devlink. This series gets that done. > > > > > > Laurent and Grygorii tested the v1 series and they saw boot time > > > improvment of about 12 seconds and 3 seconds, respectively. > > > > Now queued up to my tree. Note, I had to hand-apply patches 13 and 16 > > due to some reason (for 13, I have no idea, for 16 it was due to a > > previous patch applied to my tree that I cc:ed you on.) > > > > Verifying I got it all correct would be great :) > > A quick diff of drivers/base/core.c between driver-core-testing and my > local tree doesn't show any major diff (only some unrelated comment > fixes). So, it looks fine. > > The patch 13 conflict is probably due to having to rebase the v2 > series on top of this: > https://lore.kernel.org/lkml/20201104205431.3795207-1-saravanak@xxxxxxxxxx/ > > And looks like Patch 16 was handled fine. Great, thanks for verifying! greg k-h
