Messages in this thread | | | Subject | Re: [PATCH v1 00/18] Refactor fw_devlink to significantly improve boot time | From | Grygorii Strashko <> | Date | Fri, 6 Nov 2020 14:46:25 +0200 |
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On 06/11/2020 10:36, Saravana Kannan wrote: > On Thu, Nov 5, 2020 at 9:09 PM Laurent Pinchart > <laurent.pinchart@ideasonboard.com> wrote: >> >> Hi Saravana, >> >> Thank you for working on this ! >> >> On Wed, Nov 04, 2020 at 03:23:37PM -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. >>> >>> Tomi/Laurent/Grygorii, >>> >>> If you can test this series, that'd be great! >> >> I gave it a try, rebasing my branch from v5.9 to v5.10-rc2 first. On >> v5.10-rc2 the kernel dies when booting due to a deadlock (reported by >> lockdep, so hopefully not too hard to debug). *sigh*. Fortunately, it >> dies after the fw_devlink initialization, so I can still report results. > > Phew! For a sec I thought you said fw_devlink was causing a deadlock. > >> >> Before your series: >> >> [ 0.743065] cpuidle: using governor menu >> [ 13.350259] No ATAGs? >> >> With your series applied: >> >> [ 0.722670] cpuidle: using governor menu >> [ 1.135859] No ATAGs? >> >> That's a very clear improvement :-) > > Thanks for testing. Great to hear it's helping! > >> Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > I'll add it to my v2 series.
I've tried your series on top of 521b619acdc8 Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest on am571x-idk
Before: [ 0.049395] cpuidle: using governor menu [ 1.654766] audit: type=2000 audit(0.040:1): state=initialized audit_enabled=0 res=1 [ 2.315266] No ATAGs? [ 2.315317] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers. [ 2.315327] hw-breakpoint: maximum watchpoint size is 8 bytes. ... [ 6.549595] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null) [ 6.557794] VFS: Mounted root (ext4 filesystem) on device 179:26. [ 6.574103] devtmpfs: mounted [ 6.577749] Freeing unused kernel memory: 1024K [ 6.582433] Run /sbin/init as init process
after: [ 0.049223] cpuidle: using governor menu [ 0.095893] audit: type=2000 audit(0.040:1): state=initialized audit_enabled=0 res=1 [ 0.102958] No ATAGs? [ 0.103010] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers. [ 0.103020] hw-breakpoint: maximum watchpoint size is 8 bytes. ... [ 3.518623] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null) [ 3.526822] VFS: Mounted root (ext4 filesystem) on device 179:26. [ 3.543128] devtmpfs: mounted [ 3.546781] Freeing unused kernel memory: 1024K [ 3.551463] Run /sbin/init as init process
So, it's much better. Thank you. Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
-- Best regards, grygorii
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