On Fri, 30 Sep 2022, Rasmus Villemoes wrote: > Currently, slab_sysfs_init() is an __initcall aka device_initcall. It > is rather time-consuming; on my board it takes around 11ms. That's > about 1% of the time budget I have from U-Boot letting go and until > linux must assume responsibility of keeping the external watchdog > happy. > > There's no particular reason this would need to run at device_initcall > time, so instead make it a late_initcall to allow vital functionality > to get started a bit sooner. > > This actually ends up winning more than just those 11ms, because the > slab caches that get created during other device_initcalls (and before > my watchdog device gets probed) now don't end up doing the somewhat > expensive sysfs_slab_add() themselves. Some example lines (with > initcall_debug set) before/after: > > initcall ext4_init_fs+0x0/0x1ac returned 0 after 1386 usecs > initcall journal_init+0x0/0x138 returned 0 after 517 usecs > initcall init_fat_fs+0x0/0x68 returned 0 after 294 usecs > > initcall ext4_init_fs+0x0/0x1ac returned 0 after 240 usecs > initcall journal_init+0x0/0x138 returned 0 after 32 usecs > initcall init_fat_fs+0x0/0x68 returned 0 after 18 usecs > > Altogether, this means I now get to petting the watchdog around 17ms > sooner. [Of course, the time the other initcalls save is instead spent > in slab_sysfs_init(), which goes from 11ms to 16ms, so there's no > overall change in boot time.] > > Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
